Herbert Marshall

as Dr. Jubal Harrington

as Sir Wilfrid Lucas

as The Prime Minister

as Charles Manning

as Insp. Charas

as Robert Harley Hedges

as Insp. Mackenzie

as Stephen Collins

as Lord Leicester

as William, Earl of Mackworth

as Dr. Van Ness

as Dr. Donald L. Stanton / Narrator

as Mr. Charles Tremayne

as Dr Jameson

as E.J. Stanton

as Archibald Craven

as Willard I. Whitcombe

as Miles Rushworth

as Scott Chavez

as W. Somerset Maugham

as Traybin

as Dr. Charles Evans

as Major John Hillgrove

as Dr. Standish

as Geoffrey Wolfe

as Horace Giddens

as Rogers Woodruff

as Robert Crosbie

as Stephen Fisher

as Richard Todd

as Sir Frederick Barker

as Jonathan Blair

as Thomas Lane

as Jim Buchanan

as Gerald Shannon

as Doctor Sporum

as Walter Fane

as Arnold Ainger

as Edward 'Ned' Faraday

as Sir John Menier

as Geoffrey Hammond