Ben King and Alice Mori, friends from college and now in their late twenties, separately attend a wedding between their friends, Matt and Amanda. Having recently broken up with her boyfriend, Nate, Alice gets drunk.
Ben is fixated on former classmate Jess Ramsey and hopes to establish a romantic relationship with her. However, he embarrasses himself when she rebuffs his attempt to kiss her, as she is engaged. At the hotel, Ben and Alice vent their frustrations of having to navigate wedding season alone and decide to help one another by becoming each other’s dates. Alice also agrees to help Ben meet women at the weddings.
Ben goes golfing with his dad, Chuck, who has proposed to his much younger girlfriend, Gina, asking Ben to be his best man. Citing Chuck’s two previous failed marriages, Ben suggests his dad take some time to think about his decision. Alice uses blunt approaches to introduce Ben to various single women at the weddings, one of which culminates in Ben having a one-night-stand. However, he says that he thinks he won’t pursue anything further, remaining fixated on finding the “perfect” relationship instead of having casual flings.
After another wedding, Ben and Alice are forced to share a bed. When she attempts to cuddle with him, he feels uncomfortable. The pair attend a wedding for one of Ben’s family members, and he and Alice nearly drunkenly kiss in the pool after a deep conversation. In the conversation, Alice learns that Ben has been asked to be his dad’s best man, and expresses concern as to why he did not tell her or accept the offer.
They miss the shuttle back to the hotel and are forced to walk, eventually cutting through a cemetery. They run through the cemetery together, but Alice trips and cuts her arm. As Ben helps her, they embrace and have sex. The pair awkwardly have breakfast the following morning and decide not to discuss the previous night. Weeks later, Ben and Alice travel to Hawaii for a destination wedding and acknowledge their mutual feelings, having sex again. The pair decide to become formally romantically involved.
As Ben and Alice attend another wedding, they get into an argument over her forgetting the wedding gift, her nonchalant attitude frustrating Ben. Ben steps outside to cool off so they don’t fight publicly. Outside of the wedding, Alice confronts Ben and asks why he’s so frustrated. He confesses that he’s been having doubts about their relationship.
Ben attends the remainder of weddings alone and makes a drunken fool of himself at one of them, prompting his friend, Matt, to intervene. After some discussion about marriage not requiring 100% certainty that the relationship will work out, Ben realizes his mistake. He shows up to a wedding Alice previously invited him to, finding that she is back with Nate. He attempts to explain himself to her and professes his love, but before she can respond, Nate finds her and the two return to the wedding.
Later that night, Chuck calls Ben for a ride after taking acid during his bachelor party. Ben tells his father that his divorce is why Ben is so fixated on finding the perfect person, not wanting to make a mistake and wind up alone. Chuck explains that even though his previous marriages have failed, they still led to great things, like Ben.
At Chuck’s wedding, Ben, as the best man, gives a heartfelt speech to his dad and his new stepmother Gina. During the speech, the camera pans to reveal that Alice is there too. It’s revealed that when Ben returns home after helping his father, he finds Alice waiting for him. They kiss and get back together.
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