[s6e4] Number One Fan -

As Castle enters the clinic to negotiate, he begins to believe Emma's story despite incriminating evidence found at the crime scene, such as a murder weapon from her own kitchen and suspicious text messages. While Castle works the inside, Detective Kate Beckett and the rest of the team investigate from the outside to uncover the true killer. Key Characters & Cast

(Stana Katic): Castle's fiancée, who at the start of the episode is technically out of a job but assists the team in the investigation. [S6E4] Number One Fan

: This episode is notable for being the first time Castle is actually shot; he survives thanks to his "Writer" bulletproof vest. As Castle enters the clinic to negotiate, he

(Tom Amandes): A wealthy businessman who is revealed to be Emma's biological father. Production & Significance : This episode is notable for being the

: By the end of the episode, Beckett officially regains her job with the NYPD, ending her brief period of unemployment following her firing from the FBI. Castle season 6 episode 4 review: Number One Fan

( Nathan Fillion ): The writer-turned-investigator who must use his wits to keep the hostages safe and solve the case.