Come Undone begins during one hot, French summer in a sleepy, picturesque town near the coast of Nantes and ends there 18 months later. As Mathieu a quiet 18-year-old boy, spends yet another holiday with his depressed mother, nosy aunt and clingy sister, he meets a cocksure young man, Cedric who catches his eye while selling candy at the local seaside amusement park. The beautiful, more experienced Cedric begins to pursue Mathieu, and they are soon meeting for clandestine, evening encounters in the dunes. The young men open up to their respective families about the nature of their involvement, and a fragile happiness sets in. The audience is allowed to steal very private glances at Mathieu's memories and snapshots of his life, including his loss of innocence. These moments let us experience what happens to Mathieu after he gives in to Cedric's pleas for a life together. He learns to live independently for the first time, far removed from the people whose love he's always taken for granted.
