S4, E21: Charlie (recurring guest star KAYLEE DeFER) is finally starting to feel less like a fish-out-of-water with Serena and her friends, but complications present themselves when Charlie is invited to attend the Constance Billard alumni fundraiser. On the road to "happily ever after," Blair finds herself torn between the men in her life, and Jack Bass' (recurring guest star DESMOND HARRINGTON) return to the Upper East Side sets off a chain of events that could end up destroying Chuck and those closest to him.