Apparently a couple is having a romantic dinner, but in fact the woman is tied to the chair and the man rebukes her for cheating on him. Hours later, her body is found strangled inside a sand barge. Alice and Marquand discover that the victim was Florence Rafin, 40, a medical secretary, mother, and a follower of "Chut!", an extramarital dating app. Two similar unsolved murders in France lead investigators to think of a serial killer. During the case, Lieutenant Diacouné is having a hard time, but prefers not to share his problems with his boss, which leaves Marquand worried.
—mgallegog