Who attempted to take the life of the beauty Matilda, daughter of the well-known for his quirks and absent-mindedness professor Stendgerson? What were the motives for the crime? And, most importantly, how did the criminal manage to get into a room locked from the inside—into which, according to all the laws of physics, no one could enter—then vanish without anyone noticing? The best detectives, led by the famous inspector Larsan, are tasked with answering these questions. But only reporter Joseph Rouletabille thinks to look into the victim’s past. Being convinced that old sins cast long shadows and that there are no insoluble mysteries, the detective-journalist intends to shed light on this dark case…