Peter Killian Gallagher (born August 19, 1955) is an American actor, musician, and writer. Since 1980, Gallagher has played roles in numerous Hollywood films. He is best known for starring as Sandy Cohen in the television drama series The O.C. from 2003 to 2007, recurring roles such as Deputy Chief William Dodds on Law & Order: Special Victims Unit, Stacey Koons on the Showtime comedy-drama Californication, and Nick on the Netflix series Grace & Frankie. He also played CIA Director of Clandestine Services (DCS) Arthur Campbell on Covert Affairs.