Too weak even to miaow, the cat appeared from nowhere on New Year's Eve in a Florida family's back garden.
For six days, Barb Mazzola and her children put out food and milk, eventually coaxing the animal into their house in West Palm Beach.
They fell in love with the cat, a tortoiseshell, but when Mrs Mazzola took it to the vet, she reluctantly asked if the animal had an implanted microchip.
She did. It turned out that her name was Holly and that her owners, Jacob and Bonnie Richter, lived only a mile away.
But they had actually lost Holly two months earlier, when she bolted out of their mobile home at Daytona Beach – 200 miles north.
How Holly, who rarely ventured outside the Richters' house, managed to make the lengthy journey has baffled animal behaviourists.
It has also turned her into an internet sensation among feline aficionados and has spawned countless theories about how sights, sounds and smells, an inner compass or some memories of the drive north may have guided her.
"It is a complete mystery," said Marc Bekoff, a University of Colorado professor who specialises in animal behaviour. "She may have had some basic sense of direction and then got clues from sights or sounds as she got closer, but the truth is that we have no idea how she got home."
What seems certain, judging from the state of Holly's paws, is that she walked home.
Her back feet, the ones cats use to propel themselves, were swollen and the claws were worn down to stubs.
Mr Richter, 70, a retired airline mechanic supervisor, wonders if the cat oriented herself using the coast road.
"Evidently, she had some sort of inner sense or magic that kept her on track," he said.
Holly had clearly been eating very little on her journey as she had shed half her 13lb body weight and was severely dehydrated.