A boy is shot dead in a hotel room and a girl falls out of a window from the same room. She's still alive but the trauma has caused her a total memory loss. Davide Rivera has to rely on forensic evidence and Rex's help to track down the killer.

Two criminal brothers with a grudge against Inspector Rivera kidnap Rex and inject him with a pheromone to make him aggressive, and then use him in a series of robberies. Rex is now considered dangerous and the police are ordered to destroy him. Rivera is desperate to find Rex before the police and try to save him.