We know now who the Others are on "Lost."

They're good actors, playing good characters, and they've jogged the show's writers out of a funk.

Last week, it was revealed that "Lost" show runners Damon Lindelof and Carlton Cuse had an end date for their maddeningly enigmatic series — spring 2010, or 48 more episodes after this year's finale. Not coincidentally, this newfound clarity has coalesced during a season in which Michael Emerson and Elizabeth Mitchell have made "Lost" deeper, better, richer.

Emerson, who joined the show last season, is Ben, a bug-eyed Machiavellian leader with an elfin face and shades of L. Ron Hubbard's cult power. Mitchell, who made her debut this year, is his reluctant double-agent, a willowy beauty who's infiltrated the main castaways' beach for the somewhat-stated purpose of stealing their fertile women for the somewhat-stated purpose of populating the island so that L. Ron Ben can continue his important "work."

Their pas de deux, a mixture of deceit and empathic gesturing, is the engine driving the show's current season.

Did the writers already have big plans for Emerson, or did they see the way he stole a scene from Matthew Fox and Terry O'Quinn last year simply by eating Cheerios?

Mitchell was the star of the best episode this season, during which we learned how she got to the island, drinking a sedative and climbing into a submarine, surfacing some hours later on an island paradise.

TV shows launch as shotgun marriages with the audience but also among cast members. It's when a show becomes a hit that the producers can begin to really address the casting issues that inevitably crop up. They get to add on to the foundation, this time with more insight into the show's weaknesses.

Comedian Mary Lynn Rajskub was doubtless not on anybody's radar when "24" launched, but her addition as the deadpan Chloe has proved that the show's testosterone-fueled pace needed a different beat.

When "Lost" came on the air, it looked different — a large ensemble of faces representing numerous ethnicities. It seemed democratic and freeing, until it began to dawn on you that the show runners didn't have a main character, someone through whom the series' various themes coalesced. Locke, the cripple who could suddenly walk again, came the closest.

It's not unusual that Emerson has altered the show's tone, nor that the writers have altered their story accordingly. They'd tried Michelle Rodriguez as a militant island hottie, only to realize that she had mastered the craft of one-and-a-half expressions. They were applying roughly the same Draconian principle with which they offed castaways Shannon (Maggie Grace) and Boone (Ian Somerhalder).

Sorry, kids, it's survival of the fittest out here, in the show business sense. "Lost," by then, was fairly well covered in the eye candy department.

But it's less lousy with nuanced actors, and the story of this place demanded that new people be flown (or helicoptered, or submarined) in.

Recently, Emerson had the unenviable task of uttering this line to Locke: "John, the hesitation that you're feeling is just the part of you that still feels like (your father) has a perfectly good explanation for stealing your kidney." And he pulled it off.

You think this acting stuff's easy? Give that man an Emmy.