TONIGHT'S MUST-SEES

"Heroes" return, 8 p.m., NBC. With too many characters scattered in too many directions, this intriguing show at times has seemed scattered. Now a new storyline pulls people together: Someone is trying to capture everyone who has special abilities. That ranges from Hiro, who has lost his powers, to Sylar, who seems unstoppable. It includes Matt, who was trying to live in pleasant obscurity with super-speed Daphne. Now they're forced together. It's a good episode, with great twists — including the surprise of who is heroic enough to save the heroes.

"American Experience: The Polio Crusade," 9 p.m., PBS. The sudden devastation of polio was brutal. Lives changed overnight. Some kids recovered quickly; others were doomed to paralysis and life inside an iron lung. Emerging was an unlikely leader. Basil O'Connor had no background in science, no grasp of testing protocol. But he crafted a brilliant campaign — the "March of Dimes" — and sponsored the non-mainstream work of Jonas Salk. Others, especially Albert Sabin, said this was too rushed; a better vaccine would emerge gradually. Both researchers succeeded. Salk's vaccine was ready in 1952 and soon cut the nation's polio rate in half. Sabin's took a decade longer, but eradicated the disease. This is an epic story, with David Oshinsky's Pulitzer Prize-winning book as a prime source.

OF NOTE

"House," 7 p.m., Fox. The show's 100th episode reminds us why this may be the best show on TV. There's tragedy, a medical crisis for "Thirteen" that could ruin Foreman's career. There's comedy, as Cuddy seeks revenge on Dr. House. And there's a character issue that bounces off each person differently: What do you say to someone who has given up lifesaving to ... well, have fun?

"Chuck," 7 p.m., NBC. Dominic Monaghan, who played a former pop star in "Lost," plays a current one in this episode. (For people who have special glasses, the hour will be in 3-D.) Chuck saves the star's life, then is pulled into his party world. Meanwhile, retired football star Jerome Bettis plays an ex-con, starting work at Buy More.

"How I Met Your Mother," 7:30 p.m., CBS. Reruns have been swept aside for the "sweeps" ratings month. Tonight, Robin must get a job quickly or return to Canada.

"The Closer," 7 p.m., TNT. An obese body has been found in the trunk of the car owned by someone who stole $3 million. But the body is in such bad shape that it's hard to get more clues.

"Medium" season-opener, 9 p.m., NBC. Are visions playing tricks on our heroine? Allison keeps getting hints that the killer is the victim's first husband, who died two years earlier. There's another problem: Allison's daughter has been sent to the principal's office for making nude drawings of her art teacher.

"Trust Me," 8 p.m., TNT. In the debut, last week, Mason (Eric McCormack) hesitantly took a creative-director job at the ad agency, making him the boss of his friend Conner (Tom Cavanagh). Now the client has rejected their tagline; a new line creates complications that pull Sarah (Monica Potter) into it. It's a good episode, ranging from humor to an ethical dilemma.