A recently-married woman who has been labeled as mentally unstable, begins to suspect that someone close to her is the culprit in a sudden string of murders.

It is the end of the 18th century and smuggling is considered to be a legitimate spare-time occupation for most fishermen around the British shores. But when a gang of cut-throats, led by the infamous Black John (Bernard Lee) begins to lure ships onto the rocks of Smugglers Bay, and murdering their crews for the sake of loot, the fishermen begin to fear for their livelihoods. In desperation, they appeal to the local magistrate Squire Trevenyan (Peter Cushing).

Following World War II in peacetime Scotland, brigade headquarters replaces commanding officer Major Jock Sinclair, a boisterous battalion leader, with the strict, temperamental Lieutenant Colonel Basil Barrow. Resentful toward his replacement, Sinclair undermines Barrow's authority and damages his successor's reputation among the soldiers. Barrow faces an uphill battle in regaining the discipline and respect of his battalion.

When Watson reads from the newspaper there have been two similar murders near Whitechapel in a few days, Sherlock Holmes' sharp deductive is immediately stimulated to start its merciless method of elimination after observation of every apparently meaningless detail. He guesses right the victims must be street whores, and doesn't need long to work his way trough a pawn shop, an aristocratic family's stately home, a hospital and of course the potential suspects and (even unknowing) witnesses who are the cast of the gradually unraveled story of the murderer and his motive.