Castle (2009): Season 4, Episode 12

4 - 12: Dial M for Mayor

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.