Josh Charles, best known for his turns on Sports Night and in the film Dead Poet's Society, joins ABC's Six Degrees starting April 13, has learned. Charles will play a man from Whitney's ( Bridget Moynahan) past who will shake things up for the duration of the season, which resumes this Friday at 9 pm/ET. As part of a Six Degrees feature posting tomorrow, executive producer Stuart Zicherman describes Charles' character as "flawed, and you're not sure what he's up to," and says that he arrives on the scene in "a very McDreamy sort of way." Whoa, Mer sleeps with him, too?! She's shameless, really. For more on Six Degrees' return, watch for Friday's Interviews & Features.