The Resurrectionists

S4, E8: Father Brown is puzzled when the grave of a recent burial is opened, and the body is missing; only for it to turn up at a different undertakers. Inspector Mallory is even more mystified as the victim died of decapitation in a motor cycle accident, but shows no sign of the injury. The undertaker is arrested and the animosity between him and the victim's mother is for all to see. Father Brown uncovers the reason behind their hatred and the forbidden love the victim had for the undertaker's daughter.