Synopsis for
Forgetting Sarah Marshall (2008) More at IMDbPro »

Composer Peter Bretter (Jason Segel) is in a five-year relationship with television star Sarah Marshall (Kristen Bell), who plays the main character of a CSI-esque television show, of which Peter writes the score. One day, Sarah arrives at his house and informs him that she's leaving him. Devastated, Peter starts having sex with random strangers, but he is still unable to overcome his grief. Upon advice from his stepbrother (Bill Hader), he decides to take a trip to Hawaii and stay at a resort Sarah once mentioned; when he goes there, he is confronted by Sarah and her new boyfriend, the narcissistic English rock star Aldous Snow (Russell Brand). Seeing his plight, the sympathetic receptionist, Rachel (Mila Kunis) gives him an expensive suite provided he cleans up after himself. Peter begins his vacation weeping in his suite and drinking alcoholic beverages all day, but later begins hanging out with Rachel. After a few nights out together, Peter begins to develop feelings for Rachel. Peter also forms a tentative friendship with Aldous. Unfortunately, Peter is soon forced to vacate his suite and move into a room next door to Sarah and Aldous.

During the vacation, Sarah receives a phone-call, which informs her that her show has been cancelled. She is distraught and reveals to Peter that she fears losing her public image and fading. This incident also starts to raise tensions in Sarah and Aldous's relationship when he reveals that he intends to go on a band tour, which he hadn't told Sarah about.

One day, while out on a surfing trip with Aldous, Peter becomes angry when Aldous mentions to him that Sarah had in fact started sleeping with him a full year before the two had broken up. When Peter confronts Sarah about this, she tells him she did it because he had become lazy and she couldn't do anything to make it work, despite reading self-help books and seeking professional advice.

Sarah and Aldous' relationship deteriorates over the course of an awkward meal with Peter and Rachel. Peter and both women continue to drink to ease their discomfort, while Aldous goes on to talk about his belief in freely sleeping with any woman he meets as a way to get the most out of life. After dinner, Peter takes Rachel back to his hotel room to have sex. Sarah, who is in the room next to his, overhears them and starts to do the same with Aldous. Peter and Rachel hear them and join in the yelling, playing along like it's a game. When Aldous notices Sarah is clearly faking orgasms loudly to try and get a rise out of Peter, he stops the sex and tells her the trip was a mistake, as she's clearly not over Peter. They insult each other and their differences become very clear, prompting Aldous to call off the relationship. In the other room, Peter tells Rachel that he's really enjoyed spending time with her, and she feels the same way.

Peter encounters Aldous in the hotel lobby, who is preparing to return to England, and gives Peter a warmer farewell than he did Sarah, after harshly comparing his vacation with her to "a little holiday with Hitler" and commending Peter on having the patience to have been with Sarah for five years. Peter goes to Sarah's room to console her, but she admits she's still in love with him, and tries to rekindle their romance. After Sarah begins foreplay on him, Peter finds himself unable to continue, because she'd broken his heart and he likes Rachel now. He angrily calls Sarah the devil before storming off.

Feeling he should be honest with Rachel, he tells her what happened. Rachel tells him to leave and never to speak to her again. Peter agrees, but then visits a bar they once frequented, to remove a topless photo of her which she hated. Peter endures a beating from the bar's owner, but retrieves the photo, and wordlessly returns to the hotel to hand it back to Rachel, who is shocked.

Peter flies back to the mainland where, after a phase of self-loathing, he starts working on a Dracula rock opera, titled "A Taste for Love" and sends an invitation for the opening night to Rachel. Initially reluctant, she decides to attend the premiere. The opening night is a huge success, and Rachel congratulates Peter, also revealing that she is checking out some schools in the area to attend. They go their separate ways, until Rachel decides to go into Peter's dressing room to tell him she missed him. Peter is naked and embarrassed, as he was at the beginning of the movie, but happy as he tells her the same thing and they kiss.

During the credits, a preview is shown for Sarah Marshall's new show with Jason Bateman a detective crime drama similar to her last one, called Animal Instincts, wherein she plays a detective who is also an animal psychic.