Ellie Dunn, her father, and her fiancĂŠ are invited to one of Hesione Hushabyeâs infamous dinner parties, to be held at the house of her father, the eccentric Captain Shotover, an inventor in his late 80s who is trying to create a "psychic ray" that will destroy dynamite. The house is built in the shape of the stern of a ship. Lady Utterword, Shotover's other daughter, arrives from Australia, but he pretends not to recognise her. Hesione says they are running out of money. Shotover needs to invent a weapon of mass destruction. His last invention, a lifeboat, did not bring in much cash. Ellie intends to marry businessman Boss Mangan, but she really loves a man she met in the National Gallery. Unfortunately, her fiancĂŠ is a ruthless scoundrel, her father's a bumbling prig, and it turns out that the man she's in love with is Hector, Hesione's husband, who spends his time telling romantic lies to women. Marriage to Mangan will be the sensible choice.