A mediocre pulp novelist is approached by a stranger claiming to be a serial killer with a proposition to chronicle his crimes.

In 1958 Paris, "existentialist" crimes are being committed in the 18th arrondissement of Paris. Who is this serial killer who dares to call himself a... poet? Could it be Joseph, whom everybody in Pigalle knows as Loulou? That is at least what he accuses himself of, but who on earth could picture him as the monstrous killer?—Guy Bellinger