In Dijon, Inspector Hanaud investigates Betty Harlowe after her uncle, Boris Waberski, accuses her of poisoning her wealthy aunt for an inheritance. While an initial autopsy finds nothing, Hanaud discovers the use of Strophanthus Hispidus—a rare, undetectable poison applied via an antique arrow. Amidst a flurry of "poison pen" letters and deception, Hanaud proves the murder occurred despite the lack of conventional medical evidence.

Benita Hume
Betty Harlow

Richard Cooper
Jim Frobisher
Dennis Neilson-Terry
Inspector Hanaud
Stella Freeman
Ann Upcott
Wilfred Fletcher
Wabersky
Tony De Lungo
Maurice Thevene
Barbara Gott
Mrs. Harlow
Betty de Malero
Francine

At the Sign of the Jack'O Lantern
At the Sign of the Jack'O Lantern

Larceny
Larceny

After the Fog
After the Fog
The Open Door
The Open Door

The Circular Staircase
The Circular Staircase

Beauty and the Rogue
Beauty and the Rogue
The Great Cheque Fraud
The Great Cheque Fraud
You Never Know Your Luck
You Never Know Your Luck

It Happened in Paris
It Happened in Paris

The Girl in the Checkered Coat
The Girl in the Checkered Coat

The Mysterious Mr. Tiller
The Mysterious Mr. Tiller

Fear Not
Fear Not