Nathan Fillion, Jon Huertas, Seamus Dever Photo

From: Photo Flash: First Look - CASTLE's 'The Wild Rover,' Airing 3/25

On CASTLE's upcoming episode, titled 'The Wild Rover,' 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 and the Staten Island crime family from his days working undercover in narcotics. When the case hits a dead end, Ryan must go back undercover to expose the killer, complicating his relationship with his wife on MONDAY, MARCH 25 (10:02-11:00 p.m., ET), on ABC.