Oscar, an aloof cat kept at a US nursing home, regularly predicted patient's deaths by snuggling alongside them in their final hours.
Dr David Dosa says he initially was sceptical but his doubts disappeared after he and his colleagues tallied about 50 correct calls made by Oscar over five years.
The process is the subject of a new book - Making Rounds With Oscar: The Extraordinary Gift of an Ordinary Cat.
The feline's bizarre talent astounds Dosa, but he finds Oscar's real worth in his fierce insistence on being present when others turn away from life's most uncomfortable topic: death.
"People actually were taking great comfort in this idea, that this animal was there and might be there when their loved ones eventually pass," Dosa said.
"He was there when they couldn't be."
Dosa, 37, is a geriatrician and professor who treats patients with severe dementia. It's usually the last stop for people so ill they cannot speak or recognise their spouses, and so spend their days lost in fragments of memory.
He once feared that families would be horrified by the furry grim reaper, especially after Dosa made Oscar famous in a 2007 essay in the New England Journal of Medicine.
Instead, he says many caregivers consider Oscar a comforting presence, and some have praised him in newspaper death notices and eulogies.
"Maybe they're seeing what they want to see," he said, "but what they're seeing is a comfort to them in a real difficult time in their lives".
The nursing home adopted Oscar, a medium-haired cat with a grey and brown back and white belly, in 2005 because its staff thinks pets make the Steere House a home. They play with visiting children and prove a welcome distraction for patients and doctors alike.
After a year, the staff noticed that Oscar would spend his days pacing from room to room. He sniffed and looked at the patients but rarely spent much time with anyone - except when they had just hours to live.
He's accurate enough that the staff - including Dosa - know it's time to call family members when Oscar stretches beside their patients, who are generally too ill to notice his presence.
If kept outside the room of a dying patient, he'll scratch at doors and walls, trying to get in.
Nurses once placed Oscar in the bed of a patient they thought gravely ill. Oscar wouldn't stay put, and the staff thought his streak was broken. Turns out the medical professionals were wrong, and the patient rallied for two more days. But in the final hours, Oscar held his bedside vigil without prompting.
Dosa does not explain Oscar scientifically in his book, although he theorises the cat imitates the nurses who raised him or smells odours given off by dying cells, perhaps like some dogs who scientists say can detect cancer using their sense of scent.
Dosa says several patients in his book are partly fictional, though the names and stories of the caregivers he interviews are real and many feel guilty.
Donna Richards told Dosa that she felt guilty for putting her mother in a nursing home. She felt guilty for not visiting enough. When caring for her mother, Richards felt guilty about missing her teenage son's swimming lessons.
Richards was at her mother's bedside nonstop when she knew she was nearing her end. But after three days, a nurse persuaded her to go home for a brief rest. Despite her misgivings, Richards agreed. Her mother died a short while later.But she didn't die alone. Oscar was there.