The former "24" star will be a series regular for Season 4 of "Castle," starting with the show's season premiere Sept. 19, the network said. She will play by-the-book New York Police Department Police Captain Victoria Gates.
The character of Capt. Roy Montgomery, played by Ruben Santiago-Hudson, was killed in the series' third season finale. Gates will come to the station from Internal Affairs as his replacement.
"Penny is an actress of extraordinary depth, versatility and experience. We are delighted to have her as a part of the 'Castle' family, and look forward to everything that she's going to bring to the role," Andrew Marlowe, creator/executive producer of "Castle," said in a statement.
Returning for Season 4 will be Nathan Fillion as mystery writer Richard Castle, Stana Katic as NYPD Detective Kate Beckett, Tamala Jones as Medical Examiner Lanie Parish, Jon Huertas as NYPD Detective Javier Esposito, Seamus Dever as NYPD Detective Kevin Ryan, Susan Sullivan as Martha Rodgers, and Molly Quinn as Alexis Castle.