The painter Mario Cavaradossi helps a fugitive escape - and so attracts the attention of Scarpia, the sadistic Chief of Police. Scarpia captures Cavaradossi and has him tortured within earshot of his lover, the singer Tosca.
Scarpia sentences Cavaradossi to death - but promises Tosca that her lover can be saved if she gives herself to Scarpia. Tosca consents but as soon as the order has been given kills Scarpia. Scarpia's menace continues even in death: betrayed by a double-cross, Cavaradossi dies and Tosca leaps to her death.