Kadro (58)
Greer GarsonMarie Curie
Walter PidgeonPierre Curie
Henry TraversEugene Curie
Albert BassermannProfessor Jean Perot
Robert WalkerDavid Le Gros
C. Aubrey SmithLord Kelvin
May WhittyMadame Eugene Curie
Victor FrancenPresident of University
Elsa BassermannMadame Perot
Reginald OwenDr. Becquerel
Van JohnsonReporter
Margaret O'BrienIrene Curie - Age 5
James HiltonNarration Spoken By (voice)Mariska AldrichTall Woman (uncredited)Tony CarsonMan at Accident (uncredited)
Ruth CherringtonSwedish Queen (uncredited)
Ray CollinsLecturer (voice) (uncredited)
Guy D'EnneryProfessor (uncredited)
George DavisCart Driver (uncredited)Harold De BeckerProfessor (uncredited)Franz DorflerAssistant Tailor (uncredited)Justine DuneyWoman at Accident (uncredited)Tay DunnMan at Accident (uncredited)
William EdmundsCart Driver (uncredited)Nestor EristoffBoard Member (uncredited)
Al FergusonMan at Accident (uncredited)
Edward FieldingBoard Member (uncredited)
Howard FreemanProf. Constant (voice) (uncredited)Linda Lee GatesPerot Granddaughter (uncredited)Marie Louise GatesPerot Granddaughter (uncredited)
Lisa GolmLucille (uncredited)
Ilka GrüningSeamstress (uncredited)
Lumsden HareProfessor Roget (uncredited)
Teddy InfuhrSon (uncredited)
James KirkwoodBoard Member (uncredited)
Isabel La MalWoman at Accident (uncredited)
Gene LockhartBit Part (uncredited)
Miles ManderBusinessman (uncredited)
George MeaderSinging Professor (uncredited)Dickie MeyersMaster Michaud (uncredited)Noel MillsWedding Guest (uncredited)Leo MostovoyPhotographer (uncredited)
Alan NapierDr. Bladh (uncredited)
Moroni OlsenPresident of Businessman's Board (uncredited)María PagésWoman at Accident (uncredited)
Gigi PerreauEve at 18 Months (uncredited)
Francis PierlotMonsieur Michaud (uncredited)Nita PikeWoman at Accident (uncredited)Dorothy RayeNurse (uncredited)
Almira SessionsMadame Michaud (uncredited)
Arthur ShieldsBusinessman (uncredited)
Wyndham StandingKing Oscar (uncredited)
Ray TealDriver (uncredited)
Charles TrowbridgeBoard Member (uncredited)
Michael VisaroffProud Papa (uncredited)
Marek WindheimJewelry Salesman (uncredited)
Frederick WorlockBusinessman (uncredited)
Eustace WyattDoctor (uncredited)