Inspector Davide Rivera and Rex investigate the case of a circus animal trainer who is mauled by a tiger. The death seems accidental until Rex finds out an ultrasound whistle was used to train the tiger to attack.

When a man is found dead in his private sauna, Inspector Rivera and Rex investigate the suspicious circumstances in which the sauna door was jammed shut, causing the man to suffer a heat-induced heart attack. Soon Rivera finds that the man's mistress, his brother and his girlfriend all had a motive to kill him.