Dangerous to Know is a 1938 American crime film directed by Robert Florey and starring Anna May Wong, Akim Tamiroff and Gail Patrick. The picture is based on British crime writer Edgar Wallace's hit 1930 play, On the Spot, which had been inspired by the career of Al Capone. Anna May Wong reprised her stage role from the New York production in the movie.^[1] The supporting cast features Lloyd Nolan and Anthony Quinn.

Stephen Recka, a gangster and former bootlegger, is now a powerful figure in city politics and business circles, with the mayor and local bank in his pocket. He aspires to climb socially. A city councillor who wants to become mayor has a plant in Recka's office, John Rance, but Recka finds out.

Recka's birthday party is organized by his friend and hostess, Madame Lan Ying, with attendees who want a share in his city-wide power. Margaret van Case, an impoverished member of the "town's first family" arrives and Recka charms her, making Lan Ying unhappy.

Recka meets with Rance at his apartment. Rance is forced to write a suicide note and then falls to his death from the window. Inspector Brandon, an honest and unbribeable police officer, is now pursuing Recka for eight murders, but with no evidence to convict him.

Recka makes the mayor change the city's development plans to avoid the district around Margaret's house, as part of his plan to ingratiate himself with her. He knows Margaret's boyfriend, Philip Easton, is a bond salesman, and he buys $20,000 of bonds from him and gradually starts to give him more and more business to win his trust. Recka pursues Margaret, but Lan Ying warns him that trying to get her and enter society is reaching too far for him.

Recka brings two out of town hoods to see Phil. They steal $218,000 in bonds from his bank and kidnap him so it appears he has stolen them. The police are tipped off, and find Phil apparently drunk and the bonds missing. Recka makes an offer to Margaret to fix things and Margaret realizes Phil has been framed. Recka says he will get Phil cleared if Margaret marries him and opens the doors of respectable society for him. She agrees but vows eternal contempt for him. Phil is freed on bail.

The out of towners double cross Recka and take the bonds, but are picked up by the police for speeding. Recka realizes Phil could identify them and must be silenced. He gets plane tickets for Margaret to go away with him, but he finds the bonds have been switched for newspaper, and knows Inspector Brandon must have them.

Lan Ying understands Recka's plans and that he intends to kill Phil, but his henchman is arrested before he can complete the hit. She also knows about the plane tickets. She warns Recka she will not be waiting if he returns, and says an emotional farewell to Recka, playing a record of "Thanks for the Memory". He is confused and lonely and admits she is a real friend and the only one he can trust.

Lan Ying commits suicide with a knife. Brandon arrests Recka, intending him to be convicted as the murderer of Lan Ying and thus pay for any other crimes for which he was never tried. Recka realizes too late that Lin Yang was the one thing he needed.

Margaret and Phil fly away to their honeymoon using the plane tickets.

• Anna May Wong as Madame Lan Ying
• Akim Tamiroff as Stephen Recka
• Gail Patrick as Margaret van Case
• Lloyd Nolan as Inspector Brandon
• Harvey Stephens as Phillip Easton
• Anthony Quinn as Nicky Kusnoff
• Roscoe Karns as Duncan
• Porter Hall as Mayor Bradley
• Barlowe Borland as Butler
• Hedda Hopper as Mrs. Carson
• Hugh Sothern as Harvey Gregson
• Edward Pawley as John Rance
• Eddie Marr as Crouch
• Harry Worth as Hanley
• Robert Brister as Councilman Murkil
• Pierre Watkin as Senator Carson

Bosley Crowther of The New York Times called the film a "second-rate melodrama, hardly worthy of the talents of its generally capable cast."^[2]