17岁迷茫少女为逃避痛苦的现实，加入了一个依靠特殊神秘药物进行集体“清醒梦”的青少年团体。这群年轻人通过药物在共享的梦境中肆意狂欢，但随着用药加深，梦境与现实的边界彻底崩塌，一个隐藏在潜意识深处的恐怖黑影开始入侵现实，对他们展开无情的真实猎杀。

France in the early 60s. Simon, a wrestler, wears a white mask. In the ring, he is known as "The Specter". He suggests to his friend Victor who has just returned from combat to be his adversary in the ring and wear a black mask, and be known as "The Slaughterer of Belleville". But for Victor, still shaken from his experience in combat, this is too much; for once in his life he would like to be the good guy, the one people cheer on. Simon then suggests they switch masks. But it proves less easy to fool the rest of the wrestling crowd...