Félicien Mézeray, a wealthy Parisian art dealer, discovers an extraordinary work of art: an authentic Modigliani tattoo on the back of Legrain, a stubborn and ill-tempered former legionnaire. Convinced that the tattoo is worth a fortune, Mézeray becomes determined to acquire it at any cost. However, Legrain agrees to cooperate only if the dealer restores his country house, which turns out to be a vast, dilapidated medieval castle. What follows is a hilarious battle of wills between the cunning businessman and the eccentric old soldier, filled with unexpected complications and comic misunderstandings.