The Secret Garden

From London to Cornwall, then to Italy and France, a short, shabby priest takes on bandits, traitors and killers. Why is he so successful? The reason is that after years spent in the priesthood, Father Brown knows human nature and is not afraid of its dark side. Thus he understands criminal motivation and how to deal with it.
The Secret Garden — Father Brown is called to investigate the beheading of a man, committed in a closed garden. How did the murderer escape?
After much reflection on this