Here how Ruth Wilson left The Affair during season 4. The Affair season 1 arrived in 2014 and detailed the extramarital relationship between Alison Lockhart (Ruth Wilson) and Noah Solloway (Dominic West, The Wire). The show's unique, Rashomon-like structure played episodes from both Alison and Noah's POVs, which often resulted in drastically different takes on the same event. The show received great reviews, particularly for its performances.
The Affair season 2 took place in the aftermath of the titular affair being uncovered by their partners Helen Solloway (Maura Tierney) and Cole Lockhart (Joshua Jackson, Fringe). The Showtime series has evolved in surprising ways since it began and is set to conclude with the fifth season. The final season also introduced Anna Paquin as adult Joanie Lockhart, whose flashforward storyline is set decades on from the end of season 4.
The Affair was a great showcase for Ruth Wilson as a performer, with Alison suffering through any amount of heartbreak and disappointment over the course of the show. Part of her reason for wanting an affair was to deal with the grief of losing a child, but by the time season 4 of the show was gearing up, Ruth Wilson decided it would be her final series. Alison's story in season 4 finds her embarking on a new relationship with a marine called Ben (Ramón Rodríguez, Need For Speed). Cole also comes to realize he still loves Alison despite being in a new marriage.
Later in the season Cole and Noah team up to look for Alison after she goes missing, but later learn she has drowned from an apparent suicide. The Affair episode 9 reveals what really happened, with Alison learning Ben is married, and after a drunken confrontation, he attacks her and she bangs her head. Ben later carries her out to the ocean and throws her in, making her death look like a suicide.
It's a tragic end for the character, especially after Alison had made something of an emotional breakthrough and decided not to be a victim anymore. Ben also appears to have gotten away with his part in Alison's death, with The Affair season 5 flashforwards finding the adult Joanie - who is the same age Alison was when she died - still struggling to deal with the emotional fallout from her mother's death. Ruth Wilson has been keeping busy since departing The Affair, having returned for the fifth season of Luther and she will appear in the forthcoming His Dark Materials TV series.