The plot is discussed in detail, the way I saw it. So SPOILER ALERT ! But I guess most of you have already seen it..
It all starts with a crying baby in the arms of a woman in the packed Calcutta Metro. A police officer is looking around for a bag, or anything suspicious. Now who would suspect a woman with a baby? And that too the baby's milk bottle? The bottle breaks, a poisonous gas is realised and everyone exposed to it dies.
Fast forward two years, here comes Vidya Bagchi, a heavily pregnant women to the dirty yet beautiful and thoroughly romanticised city of joy. The police officer, Rana, is more than happy to help her, carry her bags, etc. Now, I must admit that Calcuttans are helpful people, but police? I've never met one but in movies they are always portrayed as annoying people. But then again she is pregnant, and people are always willing to help her, aren't they? It seems like an intelligent point. But as the story progressing you come to believe it is the centre of the story, the fact that she is pregnant.
Now the sad part is, she is looking for her missing husband. But there seems to be no person of that kind who ever came to India or worked where she said he worked. Ah, poor woman. How can you tell her on her face that her husband left her. She starts living in this dirty old guesthouse where she claims her husband stayed.
She randomly comes across a name, Milan Damji, who apparently resembles her husband and used to work at the same company (and he had a funny blood group, Bombay blood group). Now, the lady who told her this has to convince the adamant Vidya who is looking only for her husband that Milan does look a lot like her husband and that she should take a look at his picture before she decides not to pursue Milan Damji. That lady is murdered before she shows Vidya the photo. At this point it makes a lot of sense to kill Vidya as well. But then she is not killed. Is it because she is just a poor pregnant woman ?
When Vidya starts asking questions about Milan (again to remind you that she never wanted to look for him), the second in command of the intelligence department, Khan comes to meet her. No formality, no bureaucracy, no notices. He tells her that Milan Damji does not exist and she should drop the topic. She persists that finding Milan Damji will get her answers about her husband. He shouts at her when she insists that he is the answer to her questions. Here is where you assume a normal person would say that she has nothing to do with Milan and just wants her husband back and if Khan can help her. But Vidya continues her pursuit since Khan had called Milan Damji, Milan, so they must be close acquaintances, which means Damji exists. Very smart Vidya.
She finds her way to old company records to get the address of Milan Damji. She finds tea glasses in his house and associates it with the tea shop outside since he does not have a kitchen. Now Vidya is getting super smart. She turns up in front of Khan with the records of Milan's existence. And what does he do? He gives her top secret information that Milan was one of theirs turned over to the dark side. Now that's not protocol is it? Here you get the feeling, he is either a very stupid character or he does believe she is harmless but also that she is far more determined to find Damji and she will.
Ah, the young Rana, still helping her in every step is now in awe of her. But it turns out that he gets caught out by Khan. Rana then tries to dissuade Vidya from finding Milan. And all of a sudden starts helping her again. He gets her in contact with an old police informer. Now if he did that he could lose his job. Yes, he is likes her a lot, but would he put his career in danger for a woman who would never be his? The former police informer who refuses to help at first, but gives in when the heavily pregnant woman says she is searching for answers about her husband for her unborn baby. Yes, it's again about her pregnancy.
She gets some random information about a face-off between two people but apparently Damji was there as well and about some blood group (which I personally believe is very weird and didn't fit into the story, almost like trying to find ways of creating clues). When the try to chase up the doctor to helped with the blood, he gets killed. Again, isn't it far easier to kill her ? But yes, now the killer is looking for her as well. Our assassin, our extremely sweet, loser of an LIC agent, chubby middle aged man who can't run for a few minutes, gets killed in the chase.
Rana is freaked out for Vidya's safety and tells her that she must let the case of Damji go. Vidya doesn't seem to be listening and she is still plotting and thinking of clues. Rana asks her if death seems like a joke to her. She replies that without her husband, life itself seems like a joke to her. Sure enough. Life is a joke and death is also a joke. So much she loved her husband. So much she missed him. That without a second thought she brushed aside the idea of death. Without a second thought about her unborn baby.
She goes ahead to get more data from the tech head of the company when she find out from the tea shop outside Damji's house that the tech head used to visit him there. Rana and Vidya find their way to the tech head's office after hours, just after he leaves. But our tech head has security systems in place and his phone buzzes an alarm when his computer is turned on. He is smart too. He puts the facts together, that the receptionist is still at work, that the messenger is bringing her three glasses of water, that in the visitor's book she had an entry with visitors when he glanced at it, and rushes back to the office. Vidya has already left by then, yet the tech head catches up with them and follows them till they are caught. Rana tries to save her and fights the bad guy. Vidya here gropes for his gun going out her way. Khan arrives with back-up just as the nervous Vidya kills the tech head with his gun.
Vidya then realises that Rana was working for Khan. Khan tells her that he thought she had a better chance of getting information since no one is scared of a pregnant woman. True, isn't it? Vidya agrees to help Khan. They have by now figured out that it's Khan's boss who is helping Damji. Vidya calls up Khan's boss telling him that she has some documents she retrieved from the tech head's office that ties him up to Damji and she is ready to give it all in return for her husband. He refuses to acknowledge anything. But next moment she gets a call from Damji, asking him to meet her alone with the documents. Rana realises that she will get killed in the operation but Khan who acknowledges it calls her collateral damage and keeps Rana from telling her. Rana slips out of custody in the hope of saving her.
On the Puja Day, Vidya wears a white sari with red border that her husband had once said she should wear like all women in Bengal on auspicious days, that was gifted by Rana who requests her to wear it on the day she meets he husband since that is the most auspicious day for her. The heavily pregnant Vidya meets Milan Damji who asks her for the documents. When asks him he was Milan Damji, he says it does not matter and that she will get her husband back once they have the documents. She asks him if it is in his power to return her husband to her. He realises there is more to this woman than what seems and kicks her right in her heavily pregnant belly. She falls back, her eyes wide with shock, fear and tears of pain. And then she blinks.
She removes her fake pregnant belly, removes a pin from her hair, sticks it into his feet, grabs his gun and points to him. He asks her who she is, she says it does not matter. Shoots him and walks away. (No her sari does not slip, she is trained to tie it in such a way that once she removes her fake belly, her sari is still perfectly in place). Rana and Khan reach the spot to see Milan Damji dead, next to him is a note thanking Satyoki for his help. They can't spot a woman in white sari and red border in a street full of women dressed alike, faces covered in sindoor.
Khan is completely confused. Rana tells Khan that Vidya Bagchi is a story and she never existed. Khan wonders who Satyoki is. Rana replies that it's his real name, meaning Arjuna's sarathi, and smiles an all knowing smile !
Ah wait!The movie sadly doesn't end here.
They go back to show us the story behind Vidya from 2 years ago. Her husband was the police officer who was looking for a bag on the metro train when he was killed by the poisonous gas. Heavily pregnant Vidya loses her child when she finds out her husband is dead. The retired head of the intelligence bureau (who keeps coming up in the main lot but quite randomly) trains her to catch Milan Damji whom he created only to find out he created a monster. The movie makes sure there are no glitches by making Vidya say that having acted like she is pregnant for so long, she actually believe it was true. And then she cries saying she has no life without her husband or her baby. Ermmm. OK.