Every relationship has that 'so' moment. For a guy like Jason (Zac Efron), that's where things always end. He's firmly committed to non-commitment. When the marriage of his friend Mikey (Michael B. Jordan) falls apart, Jason takes it as proof that the single life is for the better. To get Mikey back in the game, Jason enlists him and drinking buddy Daniel (Miles Teller) to take a shared vow: together, they'll stay single as long as humanly possible. Then along comes Ellie (Imogen Poots), the unpredictable, unforgettable one-night hook-up who changes all the rules. Despite all his instincts, Jason just can't let her go and his status is about to get very complicated.