At the Grévin Museum in Paris, a historian specialising in the painter Jacques-Louis David is found murdered in the bathtub of the revolutionary Marat, a scene that replicates the master's famous painting. To unmask the murderer, Antoine Verlay and Florence Chassagne must infiltrate a symposium of art historians by posing as a couple. A cover that could well create new tensions between them. Or, on the contrary, bring them closer together...