When Richie "The Pitbull" Falco, a larger-than-life personal-injury attorney is found dead, Beckett and Castle investigate the many clients and competitors who had motive to kill him. But the mystery deepens when they discover a shocking secret that may be linked to Richie's murder.

As Castle and Alexis travel to London, their routine flight turns deadly when the plane's Air Marshal is found murdered. With the help of Beckett on the ground, Castle and Alexis race against time to find the killer before he carries out his fateful plan.