After the Barbara Loria kidnapping saga, Rex is seriously injured after attempting to shield his master from a bullet.

The corpse of a young girl is found in the pool of the dolphin at the aquatic park. Rex, Lorenzo and Morini investigate how the young girl ended up there in the first place.

Concezio Soldati takes a primary school class hostage in an attempt to avenge the death of his young son, Ivan, who was killed at the school two years earlier. Soldati holds a deep grudge against Ivan's teacher and the school's former principal.