Plot

A psychiatrist whose client commits suicide finds his family life disrupted after introducing her surviving brother to his wife and daughter.

"Every Breath You Take" is a searing psychological thriller about a psychiatrist (Casey Affleck), whose career is thrown into jeopardy when his patient takes her own life. When he invites his patient's surviving brother (Sam Claflin) into his home to meet his wife (Michelle Monaghan) and daughter, his family life is suddenly torn apart.—Vertical Entertainment

Philip Clark (Casey Affleck) is a psychiatrist who lives a strained, distant life with his wife Grace (Michelle Monaghan) and daughter Lucy (India Eisley), who are all struggling to cope with grief associated with the death of the younger child, Evan, after a car accident three years prior.

Among Philip's clients is Daphne Flagg (Emily Alyn Lind), a young depressive woman recovering from an abusive relationship, which she was able to leave with the support of Philip's therapy. Daphne is writing a book about her struggle with mental illness.

One afternoon, Philip receives a call from Daphne, who tells him that her best friend Joan has been killed in a hit-and-run accident. Later, Daphne is found dead outside her home, which the police believe to be suicide. Philip comforts her estranged British brother, James Flagg (Sam Claflin), who arrives at the scene extremely distraught. The next evening, James drops by Philip's house to drop off a book that Daphne had borrowed; sympathetic, Grace invites him to stay for dinner. Philip learns that James has written several books and is interested in buying one called Shadow Cast, which will take two weeks to arrive.

Dr. Vanessa Fanning (Veronica Ferres) confronts Philip for the unconventional methods he employed to help Daphne, which included confiding in her things that he had never shared with his family. Grace meets up with James to discuss selling his sister's house. She tells him that despite Philip's profession, he has been unable to address the pain of losing Evan and, as a result, the couple has become alienated from each other and from Lucy. Philip soon notices an inappropriate connection between his wife and James and asks James to stay away. Grace secretly goes to see James again and, despite her attempts to break off their relationship, they have sex.

James files a formal complaint against Philip with the Washington Board of Psychiatry, and Philip is suspended from his practice until it is fully investigated. James also befriends Lucy, who has a history of discipline and drug problems stemming from her grief over losing her brother, and they soon form a romantic connection. Lucy expresses a desire to run away, and James persuades her to pack her bags so they can do so together, but then later ignores her phone calls, leaving her heartbroken.

When Grace's car breaks down, James conveniently appears and offers her a ride home. He purposely misses a turn and begins driving erratically, then knocks Grace unconscious as she attempts to alert Philip. Philip chases them down and saves Grace. Back at home, they tell Lucy that James is a dangerous man but she does not believe them, obsessed by her idea of their relationship. Philip receives a call from Dr. Toth who tells him that James admitted himself to a psychiatry facility due to auditory hallucinations. Philip visits James who admits that he read Daphne's notes about her therapy with Philip, and about Philip's family background. As he is escorted back into his cell, James maniacally tells Philip that he "still smells" Grace.

Philip finally receives Shadow Cast and sees the real James Flagg on the back cover, exposing the James they have all met as an American man called Eric Dalton, Daphne's abusive ex-boyfriend. Philip discovers that Eric is psychotic; he killed Joan to make Daphne distraught in hopes that she would return to him, and when she didn't, he murdered Daphne. Philip realizes Eric has been taunting his family because Philip had helped Daphne end her relationship with Eric. Philip calls Dr. Toth to order him to lock Eric down, but Eric has already escaped after killing security guards.

Realizing that Eric is going after Lucy, Philip and Grace race back to their house. Eric attacks Lucy and, after a violent struggle, Grace kills him with the blade of Evan's old ice-skating boot. The three embrace as the police sirens approach. (thanks to Wikipedia)