Bachelor Ben and merry Alice have been friends since college. They are only friends, without any privileges and friendship sex. None of them thought about themselves as a couple. They easily discuss their sexual adventures, share the details of successful seductions and are ready to chat about all sorts of things in the evenings. In general, they have a real and almost masculine friendship. And here comes the next summer, which has prepared an unusual test for friends. Many of their friends and girlfriends decided to get married this summer. Everything is going in such a way that the heroes of the movie "Plus One" have to attend 10 weddings in the next three months! In order not to be alone, Alice invites Ben to pretend to be a real couple for a while. After a short begging, he agrees, and they go to the first solemn event. It all started out simple and carefree, but then their artificial feelings began to turn into real ones. The heroes began to try to hide them and not notice, but love is a tricky thing. She will definitely find a loophole and make lovers reconsider their attitude to friendship. Whether they will resist it is only a matter of time. It seems that the friendship of the guys will not survive this wedding season, but will it be able to transform into something more? Or will it end forever?