Provider: Eastern (ET) Change
Encoded evidence sparks Castle's imagination during the investigation into a bail bondsman's murder, but Beckett dismisses his wild theories. Meanwhile, Beckett's reunion with her ex-partner turns romantic, much to Castle's chagrin.
Castle posits time travel as a possible element in the murder of a mathematician shot by a 200-year-old bullet. A tricked-out DeLorean and a suspect in Victorian-era garb help support his theory, but a link to a secret society may explain everything.
An astrophysicist is found dead in her car, and the investigation leads Castle and Beckett to the possibility of an alien abduction. Meanwhile, a shady government agent (Lyle Lovett) tries to put an end to the pair's probe.
An investigation into a dockworker-turned-bar-owner's death leads Beckett and Castle to the city's underground tunnels, where they discover a Prohibition-era secret. The probe's focus on New York's bar history inspires Castle to open one.
Beckett and Castle tackle an upscale matchmaker's murder case, and they have company: the actress (Laura Prepon) cast as Nikki Heat, who wants a deeper grasp of her character. Her copycat image soon becomes too much for Beckett, but Castle likes it.
Beckett meets with the retired detective who handled her mom's homicide case, but he is killed right before he can tell her anything. The subsequent probe leads to a decades-old conspiracy that may reveal who murdered Beckett's mother.