A Natural History Museum employee is found dead at the foot of a dinosaur skeleton. Not a drop of water on the horizon and yet, the victim drowned.

The Japanese owner of an art gallery is found dead in a spa. Killed with a sword, he would have cut off his little finger as a sign of penance before dying as a yakuza would. Astrid and Raphaëlle go in search of a killer with a huge tattoo on his back. They will gradually realize that a family story is the key to murder.