TONIGHT'S MUST-SEE

"Day Break" debut, 8 p.m., ABC. Police Detective Brett Hopper (Taye Diggs) is a cop, on the worst day of his life. People are framing him for murder. They're trying to kill his girlfriend, Rita Shelton. And Detective Chad Shelton — Rita's former husband, Hopper's former police partner — wants to beat him up, too. Over this show's 13-hour run, Hopper will keep waking up to this same awful day. "Day Break" is superbly directed by Rob Bowman, who did the "X-Files" movie, sharply written and acted.

OF NOTE

"Dancing With the Stars" finale, 7 p.m., ABC. Last week, Joey Lawrence was voted out. Tonight, we learn whether the winner will be actor Mario Lopez or former football star Emmit Smith.

"The Biggest Loser," 7 p.m., NBC. This show nudges an hour earlier, to make room for the two-hour "Medium." Tonight, the teams are disbanded and individuals compete.

"Jericho," 7 p.m., CBS. After his heroics last week, retrieving medicine to save his father's life, Eric Green still faces trouble. He tells his wife he's leaving her for Mary. Also, he left his jacket behind. Now the vigilantes know where he is, and they plan to loot Jericho.

"Medium" season-opener, 8 p.m, NBC. The ghost of Allison's former boyfriend visits, then decides to stay — a fact that displeases her husband. Meanwhile, Allison and her daughter are having basically the same dream — except that the girl's appears via cartoons.

"CSI: NY," 9 p.m., CBS. A teen who caused an accident while driving drunk has been killed in the hospital. Was it revenge or a mercy killing?