 Professor Aristide (Basil Rathbone) runs a school for pickpockets in Paris.He takes on pupils like Yves (Mikhail Rasumny) and young Arlette (Ginger Rogers) by testing their dishonesty.He takes Arlette even though she fails by only stealing an apple instead of money; she's a runaway from a reform school where she's supposed to stay until she turns 21.