The series' misfit-y band of superheroes is back. It's been two weeks, we're told, and high-flying Peter (Milo Ventimiglia) remains in a coma. Plus, indestructible cheerleader Claire (Hayden Panettiere) is on to her evil foster dad (Jack Coleman), and stripper Niki (Ali Larter)'s murderous alter-ego could land her the death penalty. Will they and their cohorts ever unite to save Manhattan from explosion? One certainty: This essential episode is jam-packed with more than its share of romance, mayhem and fireball-worthy momentum. In fact, with so many story lines swirling, it's a wonder Heroes hasn't gone up on its own puff of combustion. But, somehow, the compelling characters, sly performances and stellar special effects converge to create a seamless wonder. Meanwhile, a new mystery man (British heartthrob Christopher Eccleston) enters the fold. Hey, the more, the merrier! (NBC, 9 P.M.)