Castle and Beckett plan a romantic weekend away in the Hamptons, but their trip turns sour when a dying man stumbles into their swimming pool. Castle is intrigued by the case and Beckett follows his lead, knowing that they will not be able to enjoy their weekend until the crime is solved. The trail leads to a retired mobster, Vincent Cardono, a drug syndicate smuggling methamphetamine out of the Hamptons and a corrupt police deputy. Meanwhile, Ryan and Esposito try to find out who Beckett's boyfriend is. Ryan discovers Castle and Beckett's secret relationship while questioning a suspect, who lets slip that he was questioned by "the writer and his girlfriend". Ryan immediately catches on, and his suspicions are confirmed when the suspect tells Ryan that Castle's girlfriend's name was "Kate".
—Anonymous