Although Napoleon’s army has been beaten by the British, two French naval officers still hold the city of Dublin under their control. The young St. Elme and his fatherly friend, Trafalgar have barricaded themselves inside a big powder keg and are threatening to blow it up as soon as there is any sign of resistance in the city. This in turn would cause the volcano looming underground to erupt and lay everything to ruins.
Katrina, an actress, seeks refuge in the house of the two old sea dogs. She has had enough of having to die every evening anew on stage. Trafalgar falls in love with her instantly. He wants to marry her and at last go to sea again with her by his side. To avoid compromising herself, Katrina hides from St. Elme, who returns from a walk to the city. St. Elme, too, is footloose and fancy-free. Unfortunately, the pretty neighbour he desires is already married. This doesn’t matter: Through his explosive arguments, he is able to convince her husband into selling his wife in accordance with traditional Anglo-Saxon law. St. Elme, however, soon finds out that the woman’s eight children were included in the bargain. In desperation, he threatens to ignite the fuse when suddenly Katrina appears and admits that she has long been in love with St. Elme. In addition, she offers him the earnings from her daily “Hamlet” performance as a dowry. Overwhelmed, St Elme agrees, and Trafalgar, too, contents himself with his paternal role as he becomes aware of the differences in age and nature between himself and the enthusiastic actress.