Fox is tinkering with its fall crime drama The Gate. Sources tell TVGuide.com that leading lady Marguerite Moreau most recently seen on The O.C. as Seth's go-to graphic-novel guru is being replaced. The Gate, which also stars fellow O.C. staple Johnny Messner and Boston Public's Chi McBride, centers on a group of detectives working at the San Francisco Police Department's Deviant Crime Unit.