Anna Khitrova (NAOMI WATTS) is a midwife at a London hospital who's just helped deliver a newborn. With the baby's teenager mother having died during delivery, Anna takes it upon herself to find the child's extended family. Yet, the only thing she has to work with is Tatiana's diary, but since it's in Russian, she can't read it. She asks her uncle Stepan (JERZY SKOLIMOWSKI) to translate it, but he thinks it's wrong to have "robbed" a dead person. Her mother, Helen (SINÉAD CUSACK), with whom she lives, however, understands her daughter's quest, especially still Anna's only child was stillborn.
Anna's quest eventually leads her to Semyon (ARMIN MUELLER-STAHL), a successful restaurateur, and underground Russian mob boss who takes an interest in translating the diary, especially when he hears that it's Tatiana's. At the same time, however, he must contend with his loose cannon son Kirill (VINCENT CASSEL), whose activities have led another mob figure, Azim (MINA E. MINA), to have a man killed. Word now is that the victim's family is headed their way for revenge, and Semyon is worried, although he knows his stoic driver, Nikolai Luzhin (VIGGO MORTENSEN), can probably handle matters.
He can, but Nikolai also shows an interest in Anna and her quest. That attention makes her uneasy, especially as she stumbles deeper into the underground world of Russian mobsters in London. Nevertheless, she continues her efforts, a pursuit that potentially endangers her life as the various elements of the mystery start coming together.