Here's a look at tonight's sci-fi TV:
Heroes, "Brave New Word" – The Heroes season finale could turn out to be a series finale thanks to tanking ratings (not to mention the show's dip in quality). Season four's final act sees Samuel taking revenge on humanity with the ultimate weapon ... a deaf girl's cello! The producers are promising a game-changing finale that will shock all 25 die-hard fans to the core. Oh, and Sylar officially becomes a good guy, again. (9 p.m. ET on NBC)
Chuck, "Chuck Versus The Mask" – It's team-up time as Morgan pairs with Elle to find out Chuck's secret, and Sarah and Shaw work together on a mission involving cute nerd couple to be (I hope) Chuck and Hannah. (8 p.m. ET on NBC)
Head after the jump for clips and more TV picks.