This NOVA program investigates the life and work of Rosalind Franklin and her unsung contribution to the discovery of the DNA helix. On April 25, 1953, the science journal Nature announced that James Watson and Francis Crick had discovered the double helix structure of DNA, the molecule that is fundamental to life. But absent from most accounts of their Nobel Prize-winning work is the contribution made by molecular biologist and crystallographer Rosalind Franklin, who would never know that Watson and Crick had seen a key piece of her data without her permission and that it would lead them to the double helix. Fifty years later, "Secret of Photo 51" unravels the mystery behind the discovery of the double helix and investigates the seminal role that Rosalind Franklin and her remarkable X-ray photograph played in one of the greatest discoveries in the history of science. Features interviews with surviving major participants in the DNA drama, including Maurice Wilkins, deputy director of the lab where Franklin worked, who casually showed her crucial Photo 51 to Watson; Raymond Gosling, Franklin's Ph.D. student with whom she made Photo 51; and Nobel Prize recipient Sir Aaron Klug, Franklin's last and closest collaborator, who inherited her notebooks. Klug analyzes Franklin's notebooks for NOVA to demonstrate just how close Franklin came to making the double helix discovery. Also appearing is award-winning biographer Brenda Maddox, author of Rosalind Franklin: The Dark Lady of which the film is partially based.