Andre Merlaux, a young officer, under the leadership of his three seniors, needs to protect and defend the interests of France and participate in dangerous operations.

When her daughter Julie disappears in the Underground Levels Under City of Paris without leaving a trace, Catherine Suzini is convinced that she alone can find it. Former cop, retired as well as drifting, she will have to resolve to team up with Raphael, the teammate of his daughter. Together, they will leave the surface and sink into the depths of Paris to embark on a terrifying and frenzied race to the descent into hell .