The charming adventurer and great botanist Louis-Guillaume Giblé de Montforty once grew the garden of his dreams in Paris. For centuries, this earthly paradise was hidden by the walls of the monastery, and now a real estate reseller is encroaching on it. His plans are fiercely opposed by rocker Lou Necker, and one day her corpse is found in Montsouris Park. Everyone believes the killer is Brad Arsenault, an American gardener with a dark past. Ingrid Diesel, however, has no more reliable friend in the world than Brad, and the appearance of an ogre, which nature has endowed him with, is not an obstacle to friendship. With her friend, ex-police commissioner Lola Jost, she undertakes to prove the gardener's innocence to the obnoxious but irresistible commissioner Dugen.