Underwater.

A police team has wired the apartment of the prime suspect in a dark serial crimes case. While there is only 6 hours left to prove his guilt, Commissioner Delattre asks Jeanne Clairsen, who works as a 'golden ear' in the Navy, to help them. Jeanne is going to embark on a sound hunt in order to prove the presence of a new victim kept captive in the suspect's home.