WHEN A WOMAN IS FOUND DEAD IN A CAR BELONGING TO THE MAYOR'S MOTOR POOL, THE INVESTIGATION THREATENS TO BRING DOWN HIS ADMINISTRATION -- AND ALSO POSSIBLY CASTLE & BECKETT'S OWN RELATIONSHIP -- ON ABC'S "CASTLE"

"Dial M for Mayor" - Derek Webster ("Desperate Housewives," "Damages") 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, on "Castle," MONDAY, JANUARY 16 (10:01-11:00 p.m., ET), on the ABC Television Network.

"Castle" stars Nathan Fillion as Richard Castle, Stana Katic as NYPD Detective Kate Beckett, Susan Sullivan as Martha Rodgers, Molly Quinn as Alexis Castle, Penny Johnson Jerald as NYPD Captain Victoria Gates, Tamala Jones as Medical Examiner Lanie Parish, Jon Huertas as NYPD Detective Javier Esposito, and Seamus Dever as NYPD Detective Kevin Ryan.

Guest Cast: Derek Webster as Mayor Robert Weldon, Adam Kulbersh as Brian Shay, Michael Grant Terry as Jordan Norris, Dave Florek as Harvey, Cara Pifko as Roberta Cambridge.

"Dial M for Mayor" was written by Christine Boylan and directed by Kate Woods.

"Castle" is broadcast in 720 Progressive (720P), ABC's selected HDTV format, with 5.1 channel surround sound. This program carries a TV-PG,D,V parental guideline.

For more information on "Castle," visit ABC.com/Castle