The Perfect Sap plot
Wealthy young Herbert Alden, a detective in training, is practicing burglary with his valet, an ex-con, when he meets George and Polly, two real thieves. They are discovered and, after a chase, they go to Herbert's city apartment. George arranges with one of them, Tony 'The Lizard', to rob the guests at a ball given by Herbert's father at his country house. Herbert discovers that Tony is actually Tracy Sutton, a much-sought celebrity engaged to Herbert's sister Roberta, and, believing Herbert to be a famous criminal, Tony asks him for advice.