* Dollhouse (8/7c Fox)'
Borrowing from the parlance of Dollhouse itself, Fox has decided to send the Joss Whedon series to the attic after its 13-episode run is up...and the network is hastening its departure by doubling up episodes this month. Tonight, the back-to-back episodes feature former Whedon hand Summer Glau (River from Firefly and Serenity) as Topher's D.C. Dollhouse counterpart, whose link to Echo results in a shocking reunion. Before that, however, Echo is assigned to stop Sen. Perrin's Dollhouse quest.
* Ugly Betty (9/8c ABC)
This episode is called "The Bahamas Triangle," but a three-sided figure doesn't begin to describe the complicated geometry of interoffice romance when the Mode staffers get away for a swimsuit photo shoot at an island resort - the same one, as it happens, used by singing sensation Shakira. Of course, nothing, including love, is ever easy for these folks, and after a few disasters and several mysterious vanishing acts, you might think they took a detour to Bermuda.
The only good news here is that everyone on the Destiny, except for one crew member, can now count on an extra portion of rations. The bad news: One crew member was found dead from a gunshot wound, and the gun was found in the quarters of Col. Young (Justin Louis). If that's not dire enough for you, there's also a planet hoarding a secret that could destroy the ship in the first-season finale.
After eight seasons, Monk is taking a final bow as the series comes to an end. Fittingly, in tonight's finale, Monk takes on the most important case of his life: solving Trudy's murder. When he finally puts the pieces together to identify the culprit, he gives it all he's got to bring the killer to justice.
* Numb3rs (10/9c CBS)
Henry Winkler reprises his role as former FBI agent Roger Bloom in this intriguing episode. Bloom is called in to help investigate when the FBI foils the robbery of an armored car carrying money from the Federal Reserve. Sounds like a pretty typical case. But the probe uncovers money that traces back to the infamous and unsolved 1971 D.B. Cooper hijacking, which Bloom investigated.