The Shadow and his agents follow a mysterious ex-convict to a small town, where he starts robbing the local captains of industry while serving a mysterious agenda based on something his dying cellmate told him.
- Evil Uncle: Hiram Maker has been the guardian of his niece and nephew since the death of their parents and clearly keeps them on a tight leash while pocketing for himself most of the proceeds from the family business their father started. He also killed their father.
- Foreshadowing: Vigilante Militia boss Eric Griffel tries to kill Slade Farrow after he is lying on the ground unconscious and helpless, establishing that he and the Shadow (who rarely kills people except in fair fights or after they have done far worse things than Farrow) are Not So Similar. This makes it a bit less surprising that he turns out to be a hoodlum posing as a vigilante.
- Good All Along: Slade Farrow and his group of shadowy ex-convicts are shown manipulating people and committing robberies throughout the book. They are actually Reformed Criminals (minus Slade, who is a sociologist who voluntarily spent two weeks in prison without committing a crime to learn to empathize with his patients) who are stealing evidence that will expose the book's real villains while taking money as well to disguise their motives and are careful to avoid violence. Given Slade and his Stealth Expert Hawkeye's role as prominent allies in many later books, and the Anachronic Order of the reprints, this is likely to come as a Late-Arrival Spoiler for many fans.
- MacGuffin: The eponymous green box is only important because it contains some mysterious papers that are taken from Farrow by vigilante Eric Griffel as soon as he finds the box in the old shop he purchased. It is later revealed that the papers are evidence against Eric and the local Corrupt Corporate Executives, which Eric gave back to his bosses. The reason Farrow spends the rest of the book robbing their homes isn't for the money but to steal back the evidence.
- Star Crossed Lover: Norton Granger is passionately in love with Mildred Legrand, but the fact that her father was accused of killing his father and died in prison causes some problems for their relationship, until it turns out Eric Griffel was the true killer and framed Mr. Legrand.
- Vigilante Militia: Eric Griffel recruits vigilantes from the athletic club and they do more to keep the town closed up to outside criminals than the police, who have to deputize them during times of trouble. Eric is really a hoodlum who covers up his actions with phony vigilantism, and while most of his men don't seem to be in on this, they are still a Trigger-Happy and easily manipulated crowd.
