A man is taking a bath in a hotel room when a stranger in a mask forces his head and drowns him under the water. This is Morgane's first case as a consultant for Lille DIPJ with Kadarec's disagreement. She is reluctant at first, but accepts the post, subject to the reopening of the investigation of her former lover Romain's disappearance, which Hazan supervises. The PJ discovers that the deceased's name was Benjamin Winckler, he was a hotel-bar regular, and he was having an affair with Gladys Puger, a doctor in her 40s who was the last person to see Benjamin alive and becomes the main suspect.