A bizarre crime happens in castle Ambrumésy in France. Thieves break into the parlour, kill a man, steal something but nothing did disappear. One of the men is trapped in the garden with no possibility to escape but can't be found, even after days of research. The investigating judge and the police are perplexed when they get unfortunate help from a grammar school pupil. A book featuring the well known gentleman-like burgler Arsène Lupin.