Having left her internship mid-way at another hospital, Dr. Nikita Malhotra (Nikki) joins Sanjeevani Hospital as an intern. There she meets her close friend from her college days, Dr. Armaan Mallik, who is doing his internship with five other interns: Dr. Riddhima Gupta, Dr. Anjali Gupta (both daughters of Dr. Shashank Gupta, Head of Sanjeevani), Dr. Atul Joshi, Dr. Rahul Garewal and his love interest Dr. Muskaan Chaddah. In the past Nikki was in love with Armaan but never told him about it. Now in Sanjeevani, Nikki finds out that Armaan and Riddhima love each other and that they don't want Anjali and the other interns to know of their relationship (except Rahul since he already knows) till they first tell Dr. Shashank about it. Riddhima and Nikki agree that Nikki should pose as Armaan's girlfriend for the time being to avoid the suspicious eyes of the others. In doing so Nikki begins to fall in love with Armaan again.
Enters Dr. Abhimanyu Modi, the young, suave, senior doctor, sent by the trustees of Sanjeevani to sort out the financial mess at Sanjeevani. He takes over from Dr. Shashank as Head of Sanjeevani and, on orders from the trustees, dismisses Dr. Keerti, the senior doctor incharge of all the interns. This annoys the interns and they hold a protest against him. Not the one to tolerate any nonsense, Dr. Modi removes a few patients whose bills have been pending for a long time making the interns even angrier. They surprise Dr. Modi with a press conference forcing him to take back the patients. Dr. Modi calmly tells the press that he has taken back the patients because the interns have agreed to pay their bills out of their own pocket. This challenge of a sorts by Dr. Modi makes the interns hunt for sources to get the money from, but all in vain; Armaan even attempts a dare devil motorcycle act but gets injured badly. Finally, they decide to hold a charity show, the "Save Sanjeevani Concert," and even manage to rope in the elusive Dr. Modi to participate in it and thereby arrange for the funds.
Whilst performing with Armaan in the concert Nikki realizes she loves him and cries bitterly when she sees him and Riddhima together which is seen by Dr. Modi. Nki later decides to leave Sanjeevani and tells Abhimanyu to discharge her but he refuses to do so. Annoyed, Nikki challenges him that in a few days he'll throw her out of Sanjeevani. Abhimanyu says he'll see to it she stays and completse her internship this time.
Nikki tries every trick possible to harass Abhimanyu but he doesn't budge. She even gets him drunk at a party, sends out SMS clips of him dancing on the road, and accuses him of forcing himself on her. Its during Holi that Abhimanyu overhears Nikki telling Anjali of her prank on Modi. Disgusted Abhimanyu decides to return the favour and gets her high on bhang (an intoxicated speciality drink of Holi). However, a change of heart makes him take care of her instead and drop her home safely. At her home, feeling protected by Abhimanyu, Nikki pours out her feelings of loneliness which melts Abhimanyu.
Thereafter Abhi-Nikki go on a medical camp trip where they share some hilarious, bickering moments. Nikki wants to go to Panchgani to help Armaan since his and Riddhima's engagement is being fixed by their parents and Armaan needs her help. Abhi tries to prevent her going on the pretext of completing her work.
Later though, Abhi surprises Nikki by taking her to Panchgani. When Abhi wants to leave for Mumbai, though, she throws away the key so as to prevent him from leaving. This sets off a chain of events leading the boys and girls to challeng each other first to a Kabaddi match and then to a game of truth and dare. A few breathtaking moments between the two during the course of the trip change the feelings they have for each other; however, they don't realize it. After the trip Abhi is completely head over heels for Nikki and imagines her everywhere.
During a client meeting, the client, Mr. Patil's lewdness towards her angers Nikki who thinks Abhi had set it up. As they argue over it, Armaan overhears them and as a protective friend fights with Abhi for Nikki. They then challenge each other to a boxing match. Armaan says if he wins then Nikki will not work in the new sanjeevani project with Abhi and if Abhi wins then she will work with him.
However, Nikki doesn't want the fight to happen because she is worried for both. She goes to Abhi and says she is willing to work with him, but he tells her that her best friend has some misunderstandings which needs to be badly cleared. On Nikki's insistence he tells her he'll not fight, but only if Armaan withdraws first. During the boxing match, whenever Abhi is injured, Nikki is in tears. Riddhima notices Nikki and Abhi exchanging emotional glances and suspects something is brewing between them. She tries to tell Armaan about it but then Abhi hits out at Armaan and wins the boxing match.
Nikki takes an injured Abhi home and tends to his wounds. He asks her why she is doing all this for him when her friend fought with him for her. Nikki has no reply. Unable to answer his questions, she asks him what exactly he wants and he says "You". To her startled expression he says he won the right over her and she angrily tells him not over her but only right to work with her and runs off.
Next day Nikki comes to know that Dr. Modi has removed her from the project and taken Riddhima instead. A jealous Nikki confronts Abhi as to why did he did he do this and he tells her at first he used to think from his heart, but now he has decided to think from his head. A misunderstanding between Armaan and Riddhima crop up because Armaan does not want Riddhima to work for Abhi and she takes it as part of her job. Eventually Abhi understands Riddhima's dilemma and lets her off the project. He reaches late for the meeting with the investors and forgets an important file. Therefore he loses the project. Nikki finds the file he had forgotten and rushes to the meeting place to give it to him. However, upset on the turn of events and losing the project, Abhi turns around and blames Nikki for it all saying its because of her, inspite of being a doctor, he is behaving like a kid. Angered by his accusation, Nikki tells him if its because of her he lost the project then she'll get the same project back for him. Abhi smirks and leaves.
She somehow convinces Mr. Patil to give them a chance. Whilst preparing for the presentation Abhi-Nikki become even more closer. They manage to get the project. However, Nikki overhears Abhi talking to his seniors about the project and not mentioning her involvement in it. This upsets her and she argues with Abhi on it.
At Dr. Keerti's pre-wedding ceremony, Abhi-Nikki are cold with each other. However, much to Nikki's surprise, Abhi still announces to everyone about them getting the project and Nikki's contribution in it. Nikki apologises to Abhi for misunderstanding him. She agrees to listen to what he wants to say, however Armaan comes and takes Nikki away spoiling their moment. Abhi then dances with Riddhima who was also upset with Armaan. Feeling jealous, Nikki ticks off Abhi saying all sorts of things which he could not understand. Unable to figure out her sudden mood swings, Abhi leaves the party annoyed. However, Nikki doesn't want him to leave. She apologises and tells him not to leave but Abhi says why should he and for whom? To which Nikki replies for her. He asks her why does she want him to stay and she says she doesn't know why. As they were having an intimate moment, Armaan interrupts them. He tells Abhi that Nikki will not go anywhere with him and even though Nikki did not agree completely with Armaan, she did not say anything. Disappointed Abhi leaves. In the car he keeps waiting for Nikki. After a long wait, he drives off. On the other hand Nikki chides Armaan and asks him to let her handle her own life. She goes in search of Abhi and is upset seeing him drive away.
Next day, inspite of the interns being given a holiday, when Abhi enters his cabin, he is surprised to see Nikki waiting for him. They end up arguing over Nikki's friendship with Armaan and Abhi leaves his cabin in a huff. While Dr. Keerti & Dr. Shubhankar's marriage preparations are going on, riots breaks out in the city. Nikki realizes Abhi is missing from the hospital and goes out in the riot in search of him. She is accosted by few goons, however, Abhi manages to save her. Seeing him bruised Nikki is in tears and they share an emotional moment where they share their fears of losing each other
When they reach Dr. Shubhankar's place, Nikki doesn't feel like getting out of Abhi's car. An emotional turbulence sweeps over her. She realizes that she is in love with Abhi. Armaan's call on Nikki's cell gets them into another heated argument . Finally Abhi manages to tell Nikki that she seems to be taking over him completely. They were about to kiss but Armaan sees them and argues with Abhi once again. However, Dr. Keerti's arrival stops their argument for the moment. Later on Riddhima asks Abhi about his feelings for Nikki and he admits he is in love with her and when she asks about Nikki's feelings, he says he feels she is too but not too sure, so would like to find out from her. Riddhima tells him she'll send Nikki to the poolside and they should talk out their feelings.
At the poolside, Abhi asks Nikki what exactly she feels for him. Does she feel the same as he does. Does she miss like how he misses her. Nikki expresses those feelings but is unable to mouth them in words. Armaan comes once again and thinks Abhi is forcing himself on Nikki and insults him. Abhi looks at Nikki to clear Armaan's doubt. However, the suddenness of the whole situation gets Nikki tongue tied and she keeps mum. Finally Armaan and the other interns insult Abhi and throw him into the pool, while Nikki watches tearfully. Hurt and humiliated, Abhi thanks her for his state and tells her he'll never forget this night ever.
Later at home Abhi is livid at being humiliated and destroys everything of Nikki's he collected as memoirs. He tells himself that this is the second time someone has trampled over his heart and he won't allow anyone come closer to it ever, not even Nikki. Sad at Abhi's humiliation Nikki cries her heart out. Later she goes to apologise to him. As Abhi sees her and hear her talk, he keeps getting reminded of his humiliation and in fit of anger insults her with a kiss. Nikki is shattered.
Back in Sanjeevani, Abhi gets stricter with the interns and even more sterner with Nikki. He burdens her with lots of work and chides her when she is unable to complete it. Nikki takes it as a self-punishment for not speaking up for Abhi. She realizes she is deeply in love with him.
At times, Abhi is vulnerable when he sees Nikki and begins to warm up towards her. He has to keep reminding himself of the decision he has taken. One such moment, when Nikki comes to his cabin to show him the project reports, they bang into each other. Watching her pick the papers that fell from his hand, he begins to soften. He tries to be stern with her but Nikki cuts out his sterness with her sweet replies. She hands over the project papers he wanted. However, as he was rushing out to a meeting, he asks Nikki to come to his place at 8pm so that they could discuss the project. Considering his softness, Nikki thinks perhaps he wanted to sort things out between them. She lands up at his place a little before the scheduled time. She apologises for the pool humiliation but Abhi is still unable to forget the incident. When Nikki touches his hand, he insults her saying that perhaps by trying to charm him she is thinking of getting her internship complete, lots of ppl do that with their seniors but he is not going to fall for it, because he doesn't think she is of his standard. He then tells her to Get Out.
Humiliated, Nikki runs out of his place and going to her house packs her bags in a bid to leave town for good. However, a debate with her inner self, makes her realize that no matter where she would go, Abhi would be with her. She wouldn't be able to remove him from within her' She finally decides to stay back and face him. She wanted to see to what extent, He would go to insult her and keep her away from him.
As Abhi briefs the interns the next morning, an eccentric (in appearance and action) girl appears before the party and declares herself to be 'Suman Lata Dalmia,' daughter of the Trustee who is funding the New Sanjivani Project. The interns are very amused to see the bizarre girl and even more so upon realizing that Dr. Modi will be working closely with her. Abhi is taken aback by Suman's behaviour but still maintains cordiality despite her antics, while the interns have a good laugh at his expense. Revitalized by her resolution from the night before, Nikki thoroughly enjoys Abhimanyu's discomfort at Suman's hands. However, only hours after having met Abhi, Suman is completely smitten with him, so much so that she decides to seek Nikki's help in wooing him. Nikki is shocked at first, but realizes that she can use Suman to get back at Abhi and revel in his uneasiness as payback for all the grief he's caused her. Soon enough, she begins manipulating events so that Abhi is constantly hounded by Suman everywhere. One day, as she and Suman are discussing a possible plan in the elevator, Abhi overhears them and becomes suspicious of the two plotting something, as he is well-aware of Nikita's mischievous nature.
Meanwhile as days pass, Abhi's anger with Nikki begins to melt away. During several encounters, Abhi instinctively ends up showing his care and protectiveness towards her. On the other hand, Nikki and Suman's pranks begin to get more vicious and Abhi becomes aware of the fact that Nikki is the one instrumenting them. On one particular occasion, he catches her red-handed and in frustration threatens to tell Suman that Nikki is only using and playing with her feelings. As Nikki rushes to stop Abhi from doing so, she falls down the stairs and fractures her foot. Shaken, Abhi scrambles to help her and takes her to a room nearby, where she is treated upon. Seeing her hurt and unconscious, Abhi's concern and love come pouring out with the fear of losing her. This incident makes him realize how much she means to him and takes away any of his remaining anger. Later, when she gains consciousness, he asks her to meet him at the badminton court, for something of a 'date.' Nikki is apprehensive upon seeing his note and remembers what had transpired between them previously, but still decides to go.
Abhi waits for Nikki at the court with a gift in hand, in mind to reform their relationship and very happy to see her finally come. However, events take a sour turn when Suman Lata decides to crash the meeting and Abhi assuming that Nikki has called her purposely, leaves in an accusatory huff. The next day, Nikki is discharged from the hospital and ordered to a week of bed rest. To her extreme horror, Suman Lata volunteers to be her care-taker and Nikki has to bear with her over-the-top antics at home, along with her injury.
As Suman is working from Nikki's home, Abhi drops by to pick up some files. Suman forces him to cook some food for them as Nikki is injured and cannot cook, while Suman has a lot of work to do. After much resistance, Abhi finally gives in, but has a very tough time trying to cook, use or find anything in the kitchen. Nikki offers her help after the blender blows up in his face and he accepts. While Nikki tries to knead the dough, they share an intimate moment which is interrupted by Suman. By now, Nikki is frustrated by her presence and the fact that she can't have Abhi alone to herself. After dinner, she puts sleeping pills in Suman's juice, hoping that the overbearing girl falls asleep and leaves her and Abhi in seclusion. On the contrary, her scheme backfires as Abhi drinks from the glass of juice she has spiked with the pills, consequently falling unconscious, into deep sleep.
The next morning, Abhi wakes up on Nikki's couch, disoriented about what happened the night before. He goes looking for her and ends up in her room. Meanwhile, Nikki who had been in shower comes out to find Abhi sitting on her bed, holding onto one of her scarves. In a vulnerable state, both of them become intimate only to be interrupted yet again.
Upon returning to work, Abhi receives a letter denoting that the funds for the New Sanjivani Project have been withheld. He calls up Suman's father, the Trustee funding the project, who tells him that he has to come to Rajhastan and meet him in person for the money to be granted. On the other end, Suman convinces Nikki to go to a wedding of her relatives in Rajhastan. Thus, as fate has it planned, Abhi, Nikki and Suman all end up going to Rajhastan together.
It turns out that Suman's father is a very stingy and money-minded man. Aware of his daughter's feelings for Abhi, he puts a proposal in front of the young doctor: the only way he will fund New Sanjivani will be if Abhi agrees to marry Suman. Put in a tight spot, Abhi decides that he has to talk to Nikki and put everything right before things become any messier. Simultaneously, Suman's leech of a brother begins making passes at Nikki and continuously harasses her, all from which Abhi saves her numerous times. Finally, Suman's brother kidnaps Nikki and this serves as the last straw for both her and Abhi, who decide to ditch the crazy family and leave Rajhastan altogether.
Stranded in a barn for the night, Nikki confesses her feelings to Abhi and both of them share some memorable moments. The union lasts momentarily though, as Abhi tells her that he is married in a shocking revelation. Shattered at being deceived so, Nikki is enraged and heartbroken. She travels to Mumbai alone and refuses to talk to Abhi despite many of his efforts. She is determined to avoid him and gives him no chance to explain his stance. Finally Abhi lands up at her house and pleads for her to hear him out. At the hospital, Nikki comes across Abhi's personal records, and among the files finds the reason why he doesn't perform surgeries, a fracture in his hand. She goes to his house and confronts him about it, but he thinks she is giving him a chance. As time passes, Nikki weakens to Abhi insistence that she give him a chance to explain himself. One day, as she is very sick, Abhi kindly offers his own cabin for her to work in and this act of his mellows her down. She asks him for a ride home and the ice between them further melts. The next day at work, Nikki finds a letter requesting divorce in Abhi's office and leaves for home. Worried because he is unable to find her anywhere, Abhi lands up at her place too and they both finally reconcile.
In the following few weeks, Abhi and Nikki share a blissful courtship until it is revealed that Abhi's wife, Jiah Modi, has refused to give him divorce. Abhi is very tense and worried due to this, but Nikki reassures him that they will get through any problems together. Just then, it happens to be that there is a terrorist attack in Sanjivani which causes the death of some of the interns. Presumably after the attack, Abhimanyu and Nikita are shown walking out of the Operation Theatre holding hands, when suddenly a woman with her wrist slit comes walking down the hall and falls into Abhimanyu's arms. The curtains on Season One of Dill Mill Gayye close as Abhimanyu is shown rushing away with Jiah Modi in his arms and Nikita is left stranded alone in the dim, cold halls of the hospital.
The story once again picks up six months after the terrorist attack in Sanjivani. During this time, Abhi and Nikki have been torn apart due to the arrival of Jiah Modi who has returned to Abhi's life. The relationship between them has boiled down to one professional alone and Nikki's demeanour towards Abhi has once again become cold and callous as he has chosen to give his wife another chance. It is revealed that Abhi is staying with Jiah because she has a mental illness and he is doing so to aid in her recovery, even though he is still in love with Nikki. Despite being well-aware of this fact, Nikki is constantly tormented by the sight of seeing the man she loves with another, while also feeling guilty herself about being the 'other woman.' Invited to his wedding anniversary, Nikki breaks down in front of Abhi and tells him to let her move on. Jiah witnesses this exchange between the two and realizes that Abhi and Nikki are in love with one another, vowing never to let them be one. Out of malice, she tries to harm Nikki by setting her saree on fire the day of Diwali and later humiliates her in front of her interns by hinting at the illicit relationship between Nikki and Abhi. When Abhi finds out about this, he is disgusted with Jiah's behaviour, who finally reveals her obsessive nature and true colours to him during a confrontation. He decides to leave her for good when she hurts herself purposely to make him stay. Using the injury from the same incident to influence Nikki into thinking that Abhi is physically abusive, Jiah's next ploy is to inject poison through misunderstandings between the two lovers.
Abhi secretly gets Nikki to come to the basketball court on the pretext of Atul calling her and finally convinces Nikki, Jiah is deliberately creating misunderstanding between them so that Nikki stops loving him. Realising her mistake, Nikki apologises to Abhi. Jiah is livid seeing Abhi and Nikki patching up. However, she doesn't give up. She wows to separate them. Whilst Nikki was walking towards her car in the Sanjeevani car park, Jiah springs up on her and tells her she has come to finish everything between Nikki and Jiah. To Nikki's horror, She pulls out a knife. Abhi was leaving for home when he hears a shrilling scream coming from the car park. When he reaches the place, he sees a terrified Nikki slowly coming out behind a car. Before he could react, he hears Jiah's painful "Abhi, Abhi." He sees her holding on to her side and fall to the ground. Terrified, he runs towards Jiah and asks her what happened and who did this to her. JIah points out to Nikki. Hearing her name Nikki drops the knife from her blood filled hands. Abhi looks disbelievingly at both of them. A ward boy yelling out "Murder, Murder" gets Abhi into action and he calls for a stretcher. He puts Jiah on it and rushes to the hospital leaving a horrified looking Nikki behind. Nikki hears the staff of Sanjeevani debating over her injuring Jiah and she feels dizzy.
Later Dr. Shashank asks Abhi whether Nikki injured Jiah and Abhi says Nikki won't do it. He needs 24 hours to find out the truth. Dr. Shashank agrees but tells him if in 24 hrs he is unable to prove anything then either Jiah or Nikki, one of them has to leave the hospital.
When Jiah has recovered a bit, Abhi visits her in her hospital room and patiently asks her what happened and who actually injured her. Jiah tells him it is Nikki. Abhi refuses to believe saying that Nikki can never do something like that. Jiah says who will believe him? She will tell the cops that Nikki has injured her and then Nikki will lose everything, her respect, her career, everything. Abhi tells her she can' do it. She tells him she won't do it if he removes Nikki completely from his life and sends her away and also not tell anyone including Nikki about this condition.
A heartbroken Abhi goes to the locker room and finds Nikki crying bitterly over the incident. He is even more sad. He sits down beside her. Nikki tells him she didn't do anything. Abhi tells her he has taken a decision and wants her to follow it. He tells her she has to leave Sanjeevani, including the city. Nikki looks disbelievingly at him. She tells him, do you think I could do such a thing? Abhi tells her it doesn't matter. Livid Nikki tells him, if he had to look into her eyes and tell her this she would still listen. For his sake she is even ready to die. Abhi blankly listens to her insults. In disgust she leaves the place leaving Abhi heartbroken. He whispers for your own safety it is important you leave Nikki. Hope one day... He is unable to continue.
When Abhi gives the good news to Jiah that Nikki has left she is on cloud nine. She tells Abhi she'll make everything right between them. A revenge seeking Abhi thinks this time he'll make it all right and he is going to be successful in it. Meanwhile Abhi gets the report from the analysts which says Jiah's wound is self inflicted. Abhi confronts Jiah about it. He tells her he won't tell anyone about it but asks her what she is going to do about the reports. He leaves, keeping a ward boy on watch over Jiah.
A heartbroken Nikki is packing her bags. She sadly looks at Abhi's framed picture caressing the glass over it while tear drops over it. She receives a call from Atul who tries to convince her not to leave but Nikki says she has had enought. The door bell rings and Nikki is shocked to see Jiah again. Jiah pulls out the knife again and tries to complete her incomplete task of killing Nikki who fearfully dodges her all over the place. In between their grappling Abhi comes there with the cops and the psychatrist who was treating Jiah. He tells Jiah not to do anything to Nikki, her game is over, everyone knows the truth about her. Holding Nikki at knife point, Jiah blurts out how she never wanted to kill Nikki instead injure her own self and put the blame on Nikki so that Abhi would be hers. However, her plan backfired, because Abhi didn't fall for it. She tells Nikki that Abhi is only hers. Realising Jiah's psychotic state of mind and the truth that Abhi never loved Jiah and instead stayed true to Nikki, gives Nikki the strength to throw a few truths at Jiah telling her how Jiah's love is not love but madness and in doing so she ruined Abhi's, Nikki's and her own life. Livid, Jiah was about to attack Nikki again when Abhi holds on to her hand and saves Nikki. Inspite of all the animosity of Jiah, he still holds her tenderly till she is tranquilised by the psychatrist while Nikki goes inside into another room. The psychatrist tells Abhi she should have listened to him earlier about Jia and the cop tells Abhi he will give his report about Jiah's condition and they take Jiah away to the asylum.
Niki and Abhi finally resolve things between themselves and Abhi proposes to her on New Years. A week or so later they have their engagement party which is arranged for them by Sid and Riddhima.