Paul and Adèle, played by Samuel Achache and Judith Chemla, two disabused extras in the opera Tristan und Isolde, make the most of a break and wander off in search of the underground lake at the Palais Garnier. It is a labyrinthine journey into the deepest recesses of the Opera, accompanied by a tortuous discussion on love, which will have the effect of a magic philtre upon them, just like the two Wagnerian protagonists. As if it were impossible to escape from legends and myths.