Rick takes on the case of Eva Whitfield who thinks her husband is cheating on her. He doesn't like cheating spouse cases but he and Eva went to high school together. He gets the photos of her husband, Cole with another woman and when he brings them to Eva, he witnesses someone dragging her bloodied body into a car and driving off.
Castle follows and tries to call Beckett but can't get a signal. When he follows someone into the woods he gets hit over the head and knocked unconscious. When he awakens he finally gets ahold of Beckett. He, Beckett and Detective Neely head back to Eva’s house but there are no signs of a struggle. Cole says Eva left a note saying she was leaving him and that he was with his mistress Taylor when Castle saw her being murdered.
When Cole says that Eva called him and took $7.4 million from their personal account, Castle begins to think that Eva might be alive and set him up, until her body is found in the Hudson river. Just as Cole is about to be arrested for her murder, he is found hanging in his home.
Castle doesn’t believe Cole committed suicide and is determined to prove it. Beckett agrees to help. It turns out that Cole was also having an affair with the wife of Robert James, one of his business partners. Robert helped Eva set Cole up for her murder. He set her up in one of their corporate apartments until she could get out of the country. But Robert has an alibi and didn’t kill Eva or Cole.
Cole’s attorney, Aubrey Haskins was sorority sisters with Cole’s first wife, who fell off a cliff while she was hiking with Cole. The police thought he killed her but didn’t have the proof to charge him with the crime. Aubrey was determined to make him pay and convinced Eva to frame him for her murder. But when Eva wanted to back out, Aubrey killed both her and Cole.
Castle is upset that he got played by an old friend and now she’s dead. He begins to wonder if he’s cut out to be a private investigator. Beckett encourages him to take some time before he makes any decisions.