24: Live Another Day (9pm, Fox) - Jack Bauer's very busy day comes to an end, thus ending the series. In the final episode, Jack works to prevent a terror plot and international crisis, but to save the world, he is faced with an unthinkable and grave decision.
Also on tonight . . .
Backpackers (8:30pm, CW) - In the premiere of this new sitcom, best friends Ryan and Brandon travel across Europe in search of Ryan's missing fiancé.
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Under the Dome (10pm, CBS) - In an episode that welcomes Dwight Yoakum for a multi-episode story arc, Chester's Mill faces a rapidly declining food supply, so Big Jim takes a census to forecast how long the town can continue to exist under the dire conditions (no doubt that creepy high school science teacher has already volunteered to um, manage, the population for him). And as if they didn't need more trouble, here comes acid rain.
Longmire (10pm, A&E) - Walt forms an unlikely alliance after Vic and Sean are kidnapped.
Murder in the First (10pm, TNT) - Six months have passed and Erich Blunt is put on trial for the murder of his flight attendant. Elsewhere, Terry tries to make amends for his behavior following his wife's death, and Hildy is tempted to rekindle a romance with her ex-husband.