Blake of Scotland Yard

Ralph Byrd

Dr. Jerry Sheehan

Herbert Rawlinson

Sir James Blake

Joan Barclay

Hope Mason

Lloyd Hughes

Dr. Marshall, 'The Scorpion'

Dickie Jones

Bobby Mason

Lucille Lund

Duchess

Nick Stuart

Julot

Sam Flint

Chief Insp. Henderson

Jimmy Aubrey

The Hag / Baron Polinka

Theodore Lorch

Daggett, the Butler