Amanda Weber (Catherine Deneuve) is a museum employee. Her nephew, Victorien (Tom Novembre), who feels that wild animals should not be kept in zoos, has been murdered, and she seeks to find out why and how. She knows that Victorien was witness to a mysterious government project where fifty tourists were killed by an unknown poison gas, and the bus in which they were travelling was found at the bottom of a lake. Alex (Richard Bohringer), a callous government assassin who is having marital problems with his wife Delphine (Sophie Moyse), has orders to kill anyone who knows about the cover-up of that project, and Amanda soon becomes his target.