“Lost” (8 p.m., ABC) attracted its largest audience of the year last week as the Oceanic Six booked a flight back to the island. It’s always risky when a series returns to its origins and asks viewers to follow. The characters on “Prison Break” seemed pretty compelling when they were tying to bust out, but once they had to break back in, fans began to drift away.

Tonight, we’re supposed to discover why Locke chose his particularly grim exit strategy. I’ve long since stopped trying to understand the totality of this wild story and its many mysteries. Instead, I like to focus on the small questions — such as what the heck happened to Ben last week? Why didn’t anyone else notice his obvious wounds and broken arm? Too bad Sawyer is still back on the island. He’d be sure to make a wisecrack about Ben’s cast.

I bring up Sawyer’s wisecracking only half in jest. “Lost” has always maintained a clever balancing act between the dark and the light, the baffling and the melodramatic, and the woo-woo and the downright funny. Over the past few weeks, we’ve encountered so many head-scratching moments and been promised so many answers that the show appears to have lost any chance for levity. Even Hurley seems driven to desperation by the latest developments. And when Hurley’s no longer good for at least one laugh, you know “Lost” has turned a serious corner.

Laughs of a dark sort can be found from the wounded Ben. When Jack asks him how he can read during a particular moment of dread, he responds cooly, “My mother taught me.” That’s a strange line coming from a man who murdered his own father. And for those taking notes, Ben seemed to be reading James Joyce’s “Ulysses,” or at least a book about the jacket design for “Ulysses.” As if you can judge a book by its cover.

• Reality contests seem to define their own reality. Only that explains why a show called “Top Chef New York” (9 p.m., Bravo) would announce its winner not in the Big Apple but the Big Easy. The show decamped for New Orleans last week when Emeril Lagasse got into the action. Fans can catch up with the entire season on a marathon beginning at 9 a.m. on Bravo.

• “America’s Ballroom Challenge” (8 p.m., PBS, check local listings) begins its fourth season with a two-hour contest pitting 24 couples against each other in every major dance style. Hosting for the first time, Jean Louisa Kelly may be remembered from her appearance in “Mr. Holland’s Opus.” Seven-time U.S. national Latin dance champion Ron Montez joins her.

Tonight’s other highlights

• A dozen hopefuls face the judges and the voting public on “American Idol” (7 p.m., Fox).

• Reese receives a tempting offer on “Life” (8 p.m., NBC).

• Smokey Robinson appears on “Spectacle” (8 p.m., Sundance) with host Elvis Costello.

• A raptor drops a ghoulish clue on the streets of Manhattan on “CSI: NY” (9 p.m., CBS).

• Sam believes he can identify a columnist’s killer on “Life on Mars” (9 p.m., ABC).

• Patty takes apart Walter’s story on “Damages” (9 p.m., FX).