When a young boy, Alwyn Jones, reports seeing a giant shiny knight in the woods, Inspector Murdoch takes an interest and walks the boy home. There, he meets Alwyn's very attractive - and widowed - mother Enid. He doesn't have much time with her however since he's called away to investigate a murder. The victim is Professor Ezra Delamore, a mathematician who now works for a major industrialist. Dr. Ogden confirms that the man was poisoned and the fatal dose was administered in a unique way. When young Alwyn disappears, they find a dwarf floating in the river while looking for him, also poisoned. Also involved in the case is the very secretive government agent Terence Meyers. Murdoch and Dr. Ogden's relationship has yet to unthaw but she seems to be coming around slowly. It all may be for naught as the detective has decided to make a social call on Mrs. Jones.