Four people in England, back in 1953, gazed at the mysterious image called Photo 51. It wasn't much--a grainy picture showing a black X. But three of these people won the Nobel Prize for figuring out what the photo really showed--the shape of DNA, the basic unit of life on Earth. The discovery brought fame and fortune to scientists James Watson, Francis Crick, and Maurice Wilkins. The fourth, the one who actually made the picture, was left out.

Her name was Rosalind Franklin. "She should have been up there," says Mary Ellen Bowden, a historian at the Chemical Heritage Foundation in Philadelphia. "If her images hadn't been there, the others couldn't have come up with the structure." One reason Franklin was missing was that she had died of cancer four years before the Nobel decision, and it can't be awarded after death. But there is a growing suspicion among scholars that Franklin was not only robbed of her life by disease but robbed of credit by her competitors. She, as much as the men around her, was first in the race to understand DNA.

Scientists knew, in the 1940s, that DNA was the thing carrying hereditary information from an organism to its descendants. But because it was too small to see directly, they had no idea how the molecule performed this feat.

So at Cambridge University in the 1950s, Watson and Crick went at it indirectly, by making models; they cut up shapes of DNA's constituents and tried to piece them together. Meanwhile, at King's College in London, Franklin and Wilkins shined X-rays at the molecule. The rays produced patterns reflecting the shape.

But Wilkins and Franklin's relationship was a lot rockier than the celebrated teamwork of Watson and Crick. Wilkins thought Franklin was hired to be his assistant. But the college actually brought her on to take over the DNA imaging project.

Which is what she did, producing X-ray pictures that, among other things, told Watson and Crick that one of their early models was inside out. And she was not shy about saying so. That antagonized Watson, who lambasted her in his 1968 book, The Double Helix: "Mere inspection suggested that she would not easily bend. By choice she did not emphasize her feminine qualities. ... Clearly Rosy had to go or be put in her place." (Other colleagues remember her as a supportive and highly skillful scientist.)

As Franklin's rivals, Watson and Wilkins had much to gain by cutting her out of the clubby little group of researchers, says science historian Pnina Abir-Am of Brandeis University. Exclusion was made easy by her gender--King's banned women from important dining rooms. And Wilkins grew closer to Watson. Close enough to show to Watson, casually, Franklin's Photo 51. "My mouth fell open," Watson wrote. That X shape was in fact a double helix, two strands wrapped around one another but running in opposite directions. This made it a biological copying machine, able to transmit mirror images of information from one cell to a daughter cell, from a parent to a child.

Watson and Crick, Wilkins, and Franklin published separate papers describing this code of life in the same 1953 issue of Nature. Franklin went on to study viruses, and then took sick, and in 1962 the others took to the Nobel podium. Wilkins gave a speech in which he thanked 13 colleagues by name before he mentioned Franklin. Watson wrote his book deriding her. Crick wrote in 1974 that "Franklin was only two steps away from the solution."

No, says Abir-Am: Franklin was the solution. "She contributed more than any other player to solving the structure of DNA. She must be considered a codiscoverer." Lynne Osman Elkin, a biographer of Franklin, agrees, saying that Franklin's notebooks show she was on to the double helix--a claim backed up by Aaron Klug, who worked with Franklin on viruses and later won a Nobel Prize himself. Once described as the "Dark Lady of DNA," Franklin is finally coming into the light.