Zeher is the story of a Goa-based police officer Siddarth(Emran Hashmi)who has parted off from his wife Sonia(Shamita Shetty) because he feels that women cannot share the same profession as men do . His co-officer James(Ninad) tries to fill up the gap between them but he fails . One day he meets a drug dealer who is along with his wife Anna(Udita Goswami) . Anna is very ill-treated by his husband , this creates some sympathy in the mind of Siddarth for Anna . Soon , this sympathy turns out into love as Anna tries to meet Siddarth when her husband is out of town . Their relationship continues when one day Siddarth comes to know that Anna is pregnant and allegedly he is the father of coming child . The doctor (Dr. Amitabh Khanna) even tells that Anna is suffering from Cancer and has 3 months to go if she is not shifted to a Cancer Hospital in Bombay . As the treatment costs were very high Anna decides to take a LIC-policy and makes Siddarth as its beneficial . Sometimes later , Siddarth comes to know from James that Anna's house is caught in fire and by the time he reaches the spot the couple had died . Then comes the twist in the story as Sonia had been assigned to investigate this death-case . Siddarth is afraid and doesn't wants Sonia to know about her relationship with Anna . He tries to wipe out every evidence that connects her with Anna . For what follows later you need to watch the movie ......