When Castle and Beckett wake up in bed, handcuffed together, in a locked room with no memory of how they got there, they must piece together the mystery of where they are and why, all while trying to escape. But as the two of them adjust to being shackled together, what's the biggest threat they face... the people who abducted them or each other? Meanwhile, Ryan, Esposito and Gates are left to investigate their disappearance in a case where all is not what it seems.

Derek Webster guest stars as Mayor Robert Weldon, Castle's longtime friend and the Mayor of New York City. It was Mayor Weldon's political clout that allowed Castle to partner up with Beckett. But now a woman is found dead in a car that traces back to the Mayor's motor pool, and that partnership comes under fire as the scandal surrounding the investigation threatens to bring down Weldon's administration.