The film portrays the events on the day King Henri III of France arranged for Duke Henri de Guise to be murdered.

Rome, June 1800. Floria Tosca is a celebrated opera singer, better known as La Tosca. Her lover is Mario Cavaradossi, a young artist and Bomapartist sympathizer. When the latter helps Angelotti, the leader of the opposition, to escape from prison and hides him in La Tosca's home, he antagonizes Baron Scarpia, the ruthless chief of police, all the more as his love for Tosca is unrequited. Scarpia has Mario arrested and condemned to death. Upset, Floria begs the Baron for her lover's life. He accepts to have the bullets of the firing squad replaced by blanks if... she sleeps with him. She agrees nominally but when she finds herself with Scarpia, she stabs him to death. She then goes to see Mario in his cell and lets him know about his phony execution. But Scarpia had had time to get the order reversed and in the early hours of the morning, Mario is executed in the proper manner. In despair, Tosca throws herself into the void...

When Troy has fallen and Ulysses sets sail for home, his ships are driven to different lands, where his adventures are numerous, keeping him away from his native land for ten years. As time rolls on without his return he is looked upon as dead by everyone except his wife, Queen Penelope, who firmly believes that her husband still lives and will some day return to her.