When a bomb explodes at a protest rally killing five people, Castle and Beckett realize the key to solving the case is to reconstruct the 47 seconds prior to the explosion. Using video and witness accounts, they uncover the shocking truth about who planted the bomb. Christine Woods (Perfect Couples) and Tim Guinee (The Good Wife) guest star. Original Air Date: Castle Season 4, Episode 19: "47 Seconds" airs on Monday, March 26, 2012 at 10 p.m. ET on ABC.