The film includes female topless nudity and scenes featuring female full frontal nudity. In one brief scene, the female's pubic area is visible. A man and woman are also shown showering together with bare breasts visible.
Mathieu is a quiet, introverted teen who feels smothered by his mother’s severe depression. During a seaside vacation, he meets Cédric, an older, confident, and openly gay young man. Their intense, passionate affair awakens Mathieu’s desires but also plunges him into a world of jealousy, heartbreak, and difficult decisions. The film is non-linear, flashing between the bliss of the summer and the painful aftermath in the fall.
The violence in "Come Undone" is largely psychological, but there are a few physical moments.