Christmas is approaching. Irene, Sherlock, and Arsène are in London. And while Sherlock is not in a good mood, as always during the holidays, a sudden mystery drags the three friends into a terrifying adventure. The director of the British Museum has been murdered under very enigmatic circumstances, and the newspapers speak of a dark curse rooted in ancient Egypt. Irene, Sherlock, and Lupin immediately begin the investigation, unraveling the thread of a very strange case whose solution, until the last moment, will be unexpected and unpredictable.