The world of this room, La Demeure Mystérieuse, is a tribute to Maurice Leblanc, the famous writer born in Rouen, who made Étretat his holiday resort and the setting for the adventures of Arsène Lupin, before acquiring the villa "le Clos Lupin" in 1919. Since 1999, this villa has been open to visitors, thanks to the initiative of Florence Boespfluq-Leblanc, the writer's only granddaughter. She had just bought the house that her father Claude, the writer's son, had sold in 1950. The La Demeure Mystérieuse room is very soothing, in different shades of green, the color most present in nature, and overlooks the garden.