Season 4 begins with terrific back-to-back episodes involving serial killers ("Assume Nothing" / "For All Our Country"). There's a new politically minded sheriff in town and in "Invisible Evidence" he's ticked off that the CSI's can't get enough evidence to convict a rapist/murderer. Also, Nick and Sara buck for the same promotion. Along the way there are plenty of quirky cases: one involving a museum robbery ("Suckers") and one involving a dead juror ("Eleven Angry Jurors"). Grissom travels to a small town with plenty of secrets to solve a murder in "Jackpot," Catherine dates a younger man in "Early Rollout," and Sara works a case involving a woman strikingly similar to herself in "Butterflied." There's also plenty of kinkiness in "Fur and Loathing" and tragedy "Bad Words."