This season of HBO's hit dramedy series finds the Fisher clan dealing with the usual complement of angst and then some. Ruth's (Frances Conroy) impulsive decision at the end of Season 3 leads to problems; Nate (Peter Krause) is wracked with grief and guilt after a tragedy; Claire (Lauren Ambrose) finds romance in an unexpected place; and David (Michael C. Hall) endures a terrifying experience that threatens to undo him.