It's almost midnight on New York's 57th St. The street is dark, except for the one light, burning in the rear of the Jonas Art Gallery. Phillip Jonas is a frustrated artist but a very successful dealer. He shows Thea Dennison a painting that he believes is valued at $40,000. She is skeptical, but she agrees to buy the painting. But then Jonas is found dead in his apartment. The painting is missing, and Mr. and Mrs. North are called in to investigate.