Olivia and Walter have been uncomfortable allies this season, and that will continue when they go "over there" together. In the alternate universe, there are rumblings that we'll meet several doppelgangers, including Walternate, who we met in the chilling '80s flashback "Peter." It won't end well, as one member of the "over here" team will die.

The season finale will include a birth, a death and a marriage proposal. Violet and Pete come to an unusual agreement in their custody battle, and Naomi and Addison reconcile.

With the Apocalypse looming, Sam and Dean pull out all the stops in a final good-versus-evil showdown. The finale will see the Winchester brothers make agonizing choices about how to stop Lucifer, which ultimately puts the life of a fan-favorite character in serious jeopardy.

Mystic Falls loves Founder's Day, what with its patriotic parade and festive fireworks and all. Johnathan Gilbert (guest star David Anders), on the other hand, is not so much a fan, so he plans to turn it into a disaster of epic proportions. Damon and Alaric will team up to stop him, but they will fail — at least the cast member who dies will see it that way.

"Salvation" will be all about redemption for Clark, as he and Zod square off when the Kandorians attack Earth. Chloe calls in some old friends to help, prompting plenty of cameos from members of the Justice League and Justice Society. Oh yeah, a major character is going to end up dead.

Wisteria Lane will be all about revealing secrets come finale time. Not only will Lynette discover the identity of the serial killer, Bree will uncover Sam's real motive and Gaby will figure out Angie's secret. With all this deception going on, someone is sure to get caught in the literal and metaphorical crossfire.

Beckett and Castle investigate the apparent assassination of an intelligence operative, but Castle's jealousy over Beckett's new beau (guest star Michael Trucco) causes tension. When Castle turns to ex-wife and book editor Gina Cowell (guest star Monet Mazur), both he and Beckett may finally realize how strong their attraction to one another really is.

The tumultuous love of Chuck and Blair will take a few more turns in the season finale when Chuck's attempts to win Blair back reach a fever pitch. And they'd better, because Blair has a new suitor, and he's in it to win it.

The doctors of Princeton Plainsboro will leave the hospital in the sixth-season finale to deal with an unusual search-and-rescue emergency. The result will have Cuddy — and everyone — looking at Dr. House in a much more positive light.

While coping with depression after the loss of her mother, Haley joins Nathan and the gang on a trip to support Julian, whose film is premiering in Utah. Looks for lots of big decisions, as Brooke and Julian's fate as a couple is decided and Naley will turn their focus to future. (The show's future, however, is still uncertain, meaning this could be your last chance to hang out with your Tree Hill pals.)

What if we told you that, after all the hand-wringing, Annie wasn't actually the driver of the car that killed Jasper's homeless uncle? We'll find out who was, and look for Teddy, Naomi, Annie and Spence Montgomery (guest star Ryan O'Neal) all to play a part in the reveal.

The final episodes of the season will attempt to recapture some of the sci-fi spookiness of the '80s original — starting with the birth of Val's alien-human baby, for example. But also look for a definitive showdown between Erica and Visitor leader Anna.

French actress Isabelle Huppert guest-stars as the mother of a kidnapped child in the season finale, which also marks the end of Sharon Stone's run as feisty DA Jo Marlowe. Before she leaves though, her plainspoken presence — and her history with Stabler — will drive a wedge between him and Benson.

Booth-Brennan fans may shed a tear or two during the season finale. "There are some big changes for them in the finale that affects the future in a big way," Emily Deschanel, who plays the title character, reveals. Executive producer Hart Hanson adds: "We have a big finale, and I hope for some more crying — of joy or sadness, I don't know."

Bill Irwin returns as Nate Haskell (aka the Dick and Jane Killer) to help Langston track down his season-long nemesis, Dr. Jekyll. The result is a brutal showdown: "Dr. Jekyll and Langston are headed for a final confrontation," executive producer Carol Mendelsohn says, "and I do not think Langston will end up unscathed." Also: The relationship between Catherine and Detective Vartann (Alex Carter) will be clarified.

Executive producer Shonda Rhimes says fans should "brace themselves" for the two-hour finale. "None of our characters are going to be the same," she adds, in particular mentioning Derek, Meredith and Cristina. Actress-singer Mandy Moore guest-stars as Bailey's patient; Ryan Devlin plays her husband.

"We're not going to catch Red John at the end of the season, but the team is going to come too close for comfort," executive producer Bruno Heller says. Meanwhile, Jane will be further tempted and fascinated by the return of Kristina Frye (guest star Leslie Hope). "Jane finds her fascinating and interesting and amusing and attractive, [but] she's doing the exact things that caused him all the tragedy in his life," Heller says. "So he's drawn to her and repelled at the same time."

Kathy Bates returns as tough-talkin' Sabre CEO Jo Bennett, and the reason for her visit is not good news for the folks at Dunder Mifflin. It ain't called "Whistleblower" for nothing: Someone is breaking the rules in selling printers, and there will be consequences.

We don't really want to know in advance what happens in the series finale of this challenging, innovative series — do you? If there's one thing Lost has excelled at over the years, it's surprising us, and why would we want to ruin that now? (Also: We have no earthly idea.) That said, you can be sure that several acts of redemption will come into play, sacrifices will be made and not everyone will get their happy ending — especially the rabid fans, who miss this show already.

As 24's clock runs out, Jack Bauer is forced to take matters into his own hands one last time. Eriq La Salle guest-stars as the charming UN Secretary General, who may have a part to play in President Taylor's world-changing plan. Executive producer Howard Gordon and star Kiefer Sutherland have promised a definitive end for Jack, but with a feature-length movie reportedly already in the works, we aren't too worried about him.

Scott Bakula will return as Chuck's dad, and it's a good thing, because he's the only person who can help when a security breach threatens everyone, especially his son. A familiar face will return, but that's not good news. But cheer up: At least Jeffster will perform!

Horatio & Co. track a serial killer who taunts the CSIs with numerous clues and bodies. Guest star Esai Morales plays the killer's apparent next target. Horatio, meanwhile, will still be reeling from what co-executive producer Barry O'Brien calls "the most dramatic betrayal in Horatio Caine's career." The end result of that betrayal may mean the end of several CSIs' careers.

This episode will survey the fallout from the Alicia-Cary competition. Eli (new series regular Alan Cumming) gears up Peter's new political career, and Alicia needs to decide if she'll be part of it or… if she'll pursue a relationship with Will. Also: Those of you still wondering for which team Kalinda plays will get your answer.

Gibbs and his team end up in Mexico for a showdown with a vengeance-seeking drug cartel. Keep your eyes out for Col. Bell (guest star Robert Patrick) to recruit some new help (Numb3rs' Dylan Bruno) in his continued aggravation of Gibbs. Ultimately, Gibbs will be forced him to make an incredible sacrifice for the sake of his team.

Callen is obsessed with finding a long-forgotten fortune that could fund a new war in the Middle East. In order to do so, he tracks down a woman who also knows quite a few jarring details about who Callen really is. Also: The team's search for missing colleague Dom will be resolved.

This guest star-heavy finale features a Los Angeles serial killer who murders entire families, save one victim who is forced to remember the horror. Tim Curry, Without a Trace's Eric Close and Profiler's Robert Davi all guest-star.

Look for another maddening cliff-hanger as Shane Casey (guest star Edward Furlong) strikes again. His targets: Danny and Lindsay. "The season finale will involve a big, big event for Danny and Lindsay," executive producer Pam Veasey says. "It's something that will make [viewers] go, 'Oh my goodness!' That will be their response." Adds cast member Hill Harper about Casey's plans: "This is such a genius way of showing how diabolical he really is. You never know what he's going to do, and that is revealed in a very dangerous way."

We don't know much about the season finale — including, for example, if it'll be the series finale as well. One hopeful sign: We'll finally arrive at the date and time of the flash-forwards, and we'll learn how each of them comes true (or doesn't, as the case may be).

If you've been waiting for Jackie to get caught for any one of her many ethical transgressions, tonight's the night! The Peytons' family vacation takes a turn for the worst when Kevin learns that Jackie took money from O'Hara. The deceived parties, Kevin and O'Hara, will join forces and suss out Jackie's drug problem as well.

It's Charmaine and Nick's wedding day. Who will show up as the bride's maid of honor? As it turns out, it'll be Tara, but that doesn't mean that everything will go smoothly, especially when Tara confronts her parents about a new memory that surfaces about her childhood.

We haven't heard much about it lately, but Quinn is in fact still pregnant and is scheduled to give birth during the season finale. Meanwhile, New Directions will have its hands full at regionals when they go head-to-head — again — with the dastardly Vocal Adrenaline. Will celebrity judges Josh Groban and Olivia Newton-John come to the gleeks' aid? Don't count on it!