The cases this season are diverse. One episode delves into the investigation of a pregnant teenage athlete's death that seems to be part of a high school "pregnancy pact," while another finds Brennan and Booth as passengers on a plane where a crisp, burnt body is discovered. And in another, Booth finds himself as the main suspect when a longtime rival is found dead. The simmering chemistry between Brennan and Booth is never lost in the intrigue. Though many TV dramas use the "will they" or "won't they" device to pique viewers' interests, that scenario usually loses momentum by the second or third season. Thanks to some smart writing and sharp acting, this conceit hasn't worn itself out yet on Bones. While the show hints that the two are destined to be together, that plot line isn't exploited this season. --Jae-Ha Kim

Stills from Bones: Season Four (Click for larger image)