We follow Francis (played by Dolan himself) and Marie (Monia Chokri), two friends who both see Nicolas (Niels Schneider) as their soul mate. At first they all just hang out together, but soon Francis and Marie are trying to one-up each other to win over Nico. That's pretty much it, but I think Dolan is wise in not letting the plot upstage the production. That is, until the end, when the movie really needs it and when a jolt of drama helps big time.
Perhaps to illuminate the story, or maybe to pad the movie up to a 95-minute running time, we also have clips of people describing their own personal love stories. The movie when it hits these patches feels a bit jerky, and these sorts of things are usually trite, but I have to say these sections actually work pretty well.
All the acting is good as well, especially Dolan, who my friend describes as almost like a silent-movie star in his emotions. He's definitely a great screen presence (apparently he acted before he started directing films), and he solidifies this late in the film when he pulls a completely unexpected move (something like a spastic convulsion) off brilliantly. "Heartbeats" will perhaps bring to mind for its viewers recent films such as "Broken Embraces" and "I Am Love." Let me tell you: it's better than both of them. B+