Poet Leonard Quinton invites Father Brown to the house where he lives with his long suffering wife Martha and young mistress Violet as his spiritual adviser Umesh has told him he will soon die and he wants the priest to look after Martha. Shortly after Violet has threatened him for not leaving Martha for her Leonard is found hanged and Umesh, as his sole heir, is arrested. Martha tells Father Brown that she and Leonard had once had a baby, born disfigured, who died and whom they buried in the garden, the event which she believes drove them apart. Martha's admirer Harris then admits to killing Leonard Quinton - though Father Brown knows better.

When the Church of Apollo comes to Kembleford, Susie is drawn to their charismatic leader Kalon. After Kalon's wife is murdered, Father Brown must break his spell over Susie or risk losing her forever.