In this crime drama an American is assigned to guard a US art exhibit in London to protect one of da Vinci's most priceless paintings, "Madonna and Child." A series of art thefts has put the museum officials on red alert and they anxiously await the painting's arrival. Unfortunately, the painting is stolen en route to the show and replaced by an imitation. The intrepid guard follows the thieves to a private gallery run by a wealthy criminal. The film contains some useful and interesting information on art forgeries.