Treadwell, the butler, quietly obsequious.

Lucia Amory, an Italian femme fatale, wife of Richard.

Aunt Caroline Amory, sister of Sir Claud, fussy with a huge heart.

Richard Amory, son of Sir Claud, a solid English gentleman.

Barbara Amory, niece of Sir Claud, spunky, daring, liberal.

Edward Raynor, secretary to Sir Claud, reserved, observant, deferring.

Dr. Carelli, a gregarious Italian, maybe a little too suave.

Sir Claud Amory, a famous inventor/physicist, patriarch, benign dictator.

Hercule Poirot, the amiable and brilliant Belgian detective.

Arthur Hastings, Poirot's trusted assistant, perceptive and self-deprecating.

Dr. Graham, a caring physician.

Inspector Japp, Scotland Yard man, fair but no-nonsense.