When struggling musician Peter Bretter (Jason Segel) is dumped by his long-term girlfriend, TV star Sarah Marshall (Kristen Bell), he goes into a downward spiral. In a last ditch effort to put the past behind him, Peter heads for the sun-soaked beaches of Oahu for a well-deserved holiday. Everything goes swimmingly until Sarah turns up at the exact same resort accompanied by her new boyfriend, the wildly successful rock star Aldous Snow (Russell Brand).