Castle - Probable Cause

Beckett's (Stana Katic) relationship with Castle (Nathan Fillion) is put to the test when all the evidence in a bizarre ritualistic killing (complete with a body stuck to the ceiling of a midtown apartment) leads back to the mystery writer. His fingerprints found at the dead woman's apartment, video evidence of Castle buying expensive jewelry for the victim, a story found on his computer that perfectly mirrors the murder, and a bag of murder gear found in the man's apartment, all tie him to the murder.

Ryan (Seamus Dever) breaks the news about Beckett and Castle's relationship to Esposito (Jon Huertas), and as the evidence mounts Beckett confides in Lanie (Tamala Jones). But despite all her angry, hurt, and frustration Beckett never believes Castle is responsible for such a grizzly murder. And despite her dislike for Castle, Captain Gates (Penny Johnson) can't quite see him as a crazed murderer, either.


Suspects not named Richard Castle include the victim's best friend (Alexa Havins) and her boss (Gerald Downey), but the real killer turns out not to have any connection to the victim at all. It turns out Castle was the real target all along as an old friend, the 3X Killer (Michael Mosley), has returned for the perfect revenge by framing Castle for murder. Learning that 3XK has put a bounty on Castle, and realizing their friend won't survive after his arraignment, Beckett, Ryan, and Esposito work around the clock to try to prove 3XK is behind the murder and frame, but before they can find the proof of his innocence Castle disappears from protective custody.

The episode does its best to sell the possibility of Castle being a killer, which we know can't be the case, but the tension works well and allows for the truth about the couple's relationship to be now known by all the regular cast members. The episode picks up with twist - the return of 3XK - and the added pressure of Beckett and her team to save Castle's life before it's too late. We're left with a final confrontation between Castle, Beckett, and the serial killer, but despite seeing the man's apparent death, Castle is quite sure they will see 3XK again.