TONIGHT'S MUST-SEE

"House" conclusion, 7 p.m., Fox. In yesterday's opener, a cop went through sudden stages — giddiness, blindness and fierce pain. Why? Dr. Foreman (Omar Epps) broke into the cop's squalid apartment to find clues. Then he began to show the same symptoms. With the men in isolation together, House faces fresh dilemmas, both medical and ethical. This would have been better at one hour instead of two, but the finale is powerful. With Charles Dutton playing Epps' dad, we see two brilliant actors in tandem.

OF NOTE

"Alias," 7 p.m., ABC. With its finale just 19 days away, this well-made show still has lots of problems to deal with. Sloane is less confident about a cure for Nadia; Anna Espinosa is still missing.

"Texas Ranch House," 8 p.m., PBS; concludes tomorrow. As yesterday's episode ended, the staff was deeply depleted. The original foreman and cook had been fired and a cowboy went home after getting word of a friend's death. Despite the troubles, there's resistance to letting Maura Finkelstein (a skilled rider) do cowboy work.

"Lost," 8 p.m., ABC. Jack, Kate and Michael return to camp with news about the Others. Meanwhile, Ana Lucia again tries to interrogate the prisoner.

"American Idol," 8 p.m., Fox. It's time to trim the field to four.

"Law & Order," 9 p.m., NBC. A political aide tips off the identity of an undercover cop. When the cop is killed, an investigation begins.

"Invasion," 9 p.m., ABC. This series started strongly with a hurricane belting the little Florida town of Homestead. Now another storm is heading that way. Meteorologist say it will miss Homestead. The "hybrids" say they're wrong.