WASHINGTON • When writer Joe Hill trained his eye on the movie Jaws, 40 years after Steven Spielberg's tale of a man-eating great white shark first smashed box-office records in the summer of 1975, he saw something that prickled his skin with goose bumps and jolted him from his seat at a movie theatre in Newington, New Hampshire.
It was not the marauding of the marine antagonist that stupefied him, but rather the fleeting appearance of an extra cast member in a crowd scene approximately 54 minutes and two seconds into the film.
The young woman seemed to have the same visage he had recently seen in a composite sketch of the victim of a grisly murder that has stumped American police on the far reaches of Cape Cod for 44 years.
One morning in late July, in 1974, a teenage girl was walking her dog along the sandy dunes of Provincetown, Massachusetts, when she came to a grove of scrub pine trees.
In a clearing lay the naked body of a woman, already badly decomposed in the summer heat. She had been between 20 and 40 years old, police estimated, when she was killed by a blow to the left side of her skull.
The authorities have never been able to figure out her identity, much less that of her killer. They exhumed her body in 2010 to create a composite sketch and she is known only as "Lady in the Dunes".
Hill, the pen name of Joe Hillstrom King and the elder son of horror writer Stephen King, believes the movie Jaws might hold a clue to the 1974 cold case.
"I felt I had seen 'Lady in the Dunes', that her face had come up out of the crowd at me," Hill said, a boyish lilt rising in his voice. "It came and went in a moment and there was no rewind button."
That evening after watching the movie, he looked on his computer to see if he could zero in on the scene, which was filmed in the summer of 1974.
But the screen on his 38cm MacBook did not yield a clear enough picture. He let it go for a while, occasionally telling friends about what he had seen.
When he mentioned the theory to a Federal Bureau of Investigation agent he knew socially, he expected the law-enforcement official to tease him.
Instead, the agent told him stranger ideas had cracked cold cases and advised him to post about it online.
He went back to the scene in question and flipped through one frame at a time. "And there she is," he said.
Hill first recorded his hypothesis on his Tumblr page in 2015, and now, a reference to his musings in a new podcast, Inside Jaws, which documents the making of the film that made Spielberg's name, has renewed interest in his theory.
At the time of production on Jaws, Hill said, film studios did not keep the same sort of records on extras that they do now.
An inquiry to an archivist at Universal Pictures made several years ago by a writer at Entertainment Weekly was unsuccessful, he said.
But he is optimistic that investigators will solve the case. "I don't think they'll ever quit," he said.
As for whether his hypothesis can help, Hill said: "I'm aware that it's probably only an interesting sort of ghost story, a tantalising 'what if?'"
Meanwhile, the idea has fascinated not only Hill, but also his father. "Everyone in my family likes a good bit of weird unsettling Americana," the writer said.
But you do not have to be a teller of horror stories to find the possibility that Jaws could bring heat to a cold case alluring, Hill insisted.
"When faced with grotesque, inexplicable tragedies, one of the ways human beings master their own anxiety and concern is by trying to reduce it to a crossword puzzle and if you have the right inspiration, you can bring order back to chaos," he said.