A multiyear search attempts to explain one of the most extreme, and baffling, cases of human survival:

On his way down, Uchikoshi lost his footing, causing him to slip, knock his head and break his pelvis. Unable to move or call for help, he lay wounded on the side of the mountain. At night the autumn cold, dropping as low as 50 degrees Fahrenheit, crept into his bones. He passed out.

After 24 days, he was found by a passing climber and transferred to Kobe City Medical Center General Hospital. He was extremely hypothermic and cold to the touch. Many of his organs were failing. According to news reports at the time, Uchikoshi’s doctors reasoned he had fallen into a state “similar to hibernation,” just like a groundhog might.

To understand his ordeal on the mountain, I would need to investigate how scientists are using extreme cold to induce a state of suspended animation in trauma patients. I would need to learn what spaceflight companies think about hibernation during interplanetary voyages, beyond the orbit of the moon and Mars, and explore how neuroscientists are unraveling the chemical mysteries inside the brain to activate hibernation-like states in other mammals. And lastly, I would need to try to find Uchikoshi.

Uchikoshi’s hibernation had become a holy grail, but it seemed like he’d become a ghost. Chasing that ghost first led me to zombies.