Anna Paquin stars in "The Affair"

One of Showtime's award-winning prestige dramas is coming to an end. On Sunday, Aug. 25, the fifth and final season of "The Affair" kicks off, and this conclusion promises to resolve the cliffhangers of Season 4 and reward fans who have been loyal to the series for five years with satisfying closure.

"The Affair" began as a relatively focused experiment that told the story of an illicit relationship between two married individuals and the consequences of said affair. The show used multiple character perspectives, flashbacks and flashforwards to unfurl the drama, and it established early on that none of the main characters were reliable narrators. It was suspenseful and subtle, and initially the story of "The Affair" was designed to be contained in a single season. The success of the experiment led to renewal after renewal, and here we are five seasons later.

The show boasts an impressive cast, and the ensemble is one of the reasons the series works so well. The series was built around the story of waitress Alison Lockhart, played by Ruth Wilson ("Jane Eyre," 2006). Alison was in a dark place after the loss of her child and made up one half of the titular affair -- the other is Noah Solloway, played by Dominic West ("The Wire"). Noah is a writer and a school teacher with what most would consider the perfect family: he has four beautiful children with his wife and first love, but, of course, all is not as rosy as it seems. While both lead characters are sympathetic, they are also deeply flawed, and neither is a particularly reliable narrator.

Two television veterans make up the supporting backbone of the series: Joshua Jackson ("Fringe") played Alison's husband, Cole, and Noah's long-suffering wife, Helen, is played by Maura Tierney ("ER"). Both struggled hard to keep their respective marriages alive, but the flashforwards reveal early on that things never get back to normal for the jilted spouses.

Fans are in for some major changes this season, but before I tell you about the losses, let me tell you what the show has gained. Yet another decorated actor from film and television has joined the cast: Anna Paquin ("True Blood") plays the grown-up version of Alison and Cole's daughter, Joanie.

Now to the losses. The aforementioned cliffhanger was about as big as they get for a television show: Alison was found dead after an apparently successful suicide, but in the penultimate episode of the season, it was revealed that she had actually been murdered. The sad details of Alison's life and death are sure to affect all of the characters in a big way in Season 5, but a grown-up Joanie will be especially interesting to watch. Whether the crime will be solved remains to be seen.

Killing off a lead character is obviously a huge risk for a show to take, but in this particular case, it was unavoidable: Wilson asked to leave the show, so the writers were forced to find a way for Alison to disappear. Thanks to the myriad of questionable and self-destructive decisions the character has made over the course of the series, there were likely a lot of options.

Maura Tierney stars in "The Affair"

Wilson has been diplomatically (or strategically?) coy about her exact reasons for departing. The issue of pay parity has come up in several interviews, but in subsequent comments she clarified that she never discussed the matter of compensation with the show's producers. In an interview with the New York Times, Wilson said, "It isn’t about pay parity, and it wasn't about other jobs. But I'm not really allowed to talk about it. There is a much bigger story." A mystery, it seems.

The mystery deepened when it was announced earlier this year that Jackson would not be returning to the show, either. His reasons are even more mysterious -- Jackson hasn't commented at all on his departure, and some fans suspect it was an act of solidarity with Wilson. Whatever the secret reasons for the pair's exit, there's no disputing that Season 5 of "The Affair" will be a significantly different show.

The forecast for Season 5 isn't all about losses, though. Paquin's arrival is welcome news for fans, and her character's story arc adds a new gambit to "The Affair's" bag of tricks. With two absent parents and significant trauma in her past, Joanie is sure to be a fascinating character. It's a shame we'll only get one season to get to know her. The timeline-twisting narrative devices the series uses will continue, and fans will get to keep speculating about which character's experiences come closest to the truth. It isn't always easy for a longstanding series to introduce a major new character this late into its lifespan, but many are predicting Paquin will carry the last season's ups and downs without a hitch.

The final season of "The Affair" begins Sunday, Aug. 25, on Showtime.