German-American Los Angeles–based detective Fritz Brown is hired by the mysterious caddie Fat Dog Baker, who wants him to spy on his sister Jane and her benefactor, the much older businessman Sol Kupferman.

Brown suspects Fat Dog of being an arsonist and discovers that Kupferman owned Club Utopia through a proxy.

Brown, thinking there might be a connection between the two men, decides to look for Fat Dog, who has disappeared and force him to confess but finds him dead in Mexico instead.

Brown finds it and learns how Fat Dog, apart from the Utopia arson, had burned the houses where he had lived as foster child with his sister.

To avoid scandal after Louisa's suicide, Kupferman gave the children to foster parents and bribed a corrupt officer, Haywood Cathcart, for buying his silence about the matter.