An amnesia is collected and cared for by a couple of pensioners, Abe and Sally. He has a XIII tattooed on the collarbone. The couple is murdered by two men whom XIII kills. On one of them, he finds a photo showing him with a young woman... A solid boy with the appearance of a barouder finds himself without name, without past, without memory, in an unknown place. His only beginning of clue to discover his identity is a number, XIII, which he wears in tattoo. His position is all the more uncomfortable as a gang of killers is at his disposal. Moreover, he discovers that high civilian and military personalities are interested in him.