When a man is found dead in an industrial cake mixer, Castle and Beckett trace the murder to an Irish gang in Staten Island and a beautiful bar owner named Siobhan O'Doul (guest star Cara Buono, "Mad Men"
). Much to everyone's surprise, Detective Ryan has a complicated history with Siobhan from his days working undercover in narcotics. Ryan must go back undercover to expose the killer. Full Episode Details »