S4, E17: Ben's (recurring guest star DAVID CALL) mother (guest star MARSHA DIETLEIN BENNETT – Little Children) comes to town, forcing issues to the surface between Ben and Serena. Meanwhile, Russell Thorpe (recurring guest star MICHAEL BOATMAN) is determined to destroy Chuck's family legacy, but he risks alienating his daughter, Raina (recurring guest star TIKA SUMPTER), in the process. Plus, recurring guest star BILLY BALDWIN appears as William van der Woodsen, Lily's ex-husband and Serena and Eric's father.