as John McLaren
as Katy Dandridge
as Mary McLaren
as Professor Herbert Weisse
as Peter Leduq
as Randowsky
as Sergei Boetnikov
as General van Dorff (uncredited)
as Dennis McLaren (uncredited)
as Lab Assistant (uncredited)
as Stuart (uncredited)
as Landowsky (uncredited)
as John McLaren (uncredited) (voice)