Dick Arrowsmith
Ethel
Samuel Wolfe
Layons
Garreth
Bill Steer
Engineer Nikitin
Sazonov
Gaydar
Bistayev
Comrade Olga
Gostev
Rakitin
Rector (uncredited)
Professor (uncredited)
Felice (uncredited)
John's wife
Laboratory worker (uncredited)
Arrowsmith's guest
Arrowsmith's guest
The reporter (uncredited)
The worker (uncredited)
The provocator (uncredited)