On the night of a college party, in a fit of anger, Tanya downloads the Knock Knock app and puts a death wish on Mehek setting off a series of unfortunate events.
Tanya is blackmailed into a task for the Knock Knock Killer as Mehek is found in a near death condition.
Tanya meets a mysterious and brooding stranger - Adheer. Knock Knock warns Tanya that someone close to her will pay for the task she left incomplete.
Tanya is chased and pulled under water as the Knock Knock Killer attacks her.
The gang discovers Adheer dragging Tanya out of the lake. Is he the killer or her savior?
Tanya finds an ally in Adheer who believes in her. At the vigil for Mehek, a shocking arrest is made.
Everyone is relieved the Knock Knock Killer has been caught, But Tanya is chased and attacked by Knock Knock at the same time!
The gang plans a romantic date for Tanya and Adheer in an attempt to find out more about Adheer. Richa and Random find out a shocking secret about Adheer at the hostel.
Vicky keeps a watch on Adheer, their prime suspect as Tanya and Richa go to Simi's house and find out a shocking secret about her.
Just when things seem clear, Knock Knock gives Tanya another task to save one of her friends. And this time, it is deadly.
Tanya's plan backfires as Knock Knock sees through the deception and Knock Knock attempts to get away.
Tanya and Rohan realize Knock Knock is trying to set up not only Tanya, but Rohan also.
Ammonia's body is found and Knock Knock attacks Mehek in Tanya's house. The gang gives chase and finally find the real Knock Knock Killer.
The mystery is solved and everyone gets together. Kavita finds a shocking clue about his past and Tanya realizes maybe she doesn't know her friends all that well.
The Knock Knock Killer is at a party and Tanya finally manages to corner him. And is shocked to see who it is.
Knock Knock takes Tanya on a journey to the past and explains why he did all that he did.