Neville and Roger Shandon are twin brothers who live, along with a few other family members, at a country estate. While they look alike, they have quite different backgrounds: Neville is a highly successful lawyer while Roger seems to have been some sort of adventurer or explorer in South America.

Frustrated with their noisy family members, the brothers decide they have need of some peace and quiet, so they each visit the large hedge maze on their property which has two separate, secluded centers where they hope they can sit undisturbed. Two house guests decide that they will also have some fun in the maze, setting out to try to race each other to the center. When they reach the centers, however, they discover that both brothers have been murdered.

Sir Clinton Driffield is the local chief constable who investigates the crime with the help of Squire Wendover and they quickly establish that each twin was shot by a poisoned dart laced with curare - a poison used on arrows in South America. It turns out that there had been a jar of the arrow poison left unsecured on the grounds of the house. As Sir Clinton notes, everyone had access to the murder weapon and, because the weapon does not require any great strength, even a woman might have done the crime....