The Case of the Scorpion's Tail begins with the mysterious death of a millionaire and spirals into the murder of his suddenly rich wife, which draws the attention of a dogged investigator, who follows a trail of blood to the bitter end.

The film centers on a Spanish tapas bar and the love lives of the loosely interconnected people in the neighborhood surrounding the bar. The pairs of lovers include a middle aged woman and a young man; an elderly, drug dealing woman and her terminally ill husband in poor health; the tapas bar owner and his estranged wife; and two Chinese immigrants.

Mysterious and unearthly deaths start to occur while Professor Saxton is transporting the frozen remains of a primitive humanoid creature he found in Manchuria back to Europe.