Returning to England for his brother's funeral, Stephen Ezard (Benedict Cumberbatch) falls in love with his brother's widow, Yasim (Anamaria Marinca), becomes a pawn in a government surveillance scheme, and is pursued by a crazed rogue agent (Robert Carlyle).

Noted microbiologists are dying at an alarming rate as Stephen tries to learn the cause of death of the beautiful woman found in his apartment. Yasim suspects that her late husband, Michael, stumbled on the secret before being blown up by a landmine in Afghanistan.

Sent to retrieve blood samples from refugees dying from the contaminated vaccine, Stephen has a startling revelation that sends him racing to expose the truth before all evidence is destroyed.