A dead body found floating in a lake... Unexplained scratch marks on her neck... Supari killers out to kill her... A taxi driver who yells 'bhoot, bhoot' every time he sees her...Sehar's (Ayesha Takia) world turns topsy-turvy when she gets a clue about the missing Sunday of her life, which points to a possible violent attack on her. A.C.P Rajveer (Ajay Devgan) takes up the case to sort out the complicated and jumbled up threads of Sehar's life. In the process of solving Sehar's case it comes to light that on Sunday, different people interacted with her and amongst them, one could be the accused. The lot included Ballu (Arshad Warsi), the taxi driver and his friend, Kumar (Irrfan Khan), a struggling NSD actor, Ritu (Anjana Sukhani), Sehar's close friend, a scary and suspicious character who resides in Sehar's society, and the group whom she had come across while partying at the discotheque. While trying to solve the puzzle, Rajveer stumbles upon a murder case whose clues hold up Sehar to be the culprit. Seher is at first amused, then mystified and then terrified when she realises she has a connection with all these totally unconnected incidents. But she cannot remember anything, Her fiancée ACP Rajvir Randhava is convinced that Seher is innocent, but he is also equally sure that she is linked to everything. Then another dead body is found. And the bracelet found near the corpse belongs to Seher. The evidence is mounting and all dingers point ay Seher. And still, Seher does not remember anything. Is Seher really as innocent as she claims to be? A dubbing artiste by day, is she also a serial killer by night? Is her bubbly charm but a mask that hides her darker, menacing self? As Seher desperately fights the fog that clouds her treacherous memory, ACP Rajvir has to fight the fact that the woman he wants to marry may well be a murderer and worse...What if one day went missing from your life?