Whether her core temperature had ever approached the level at which the heart typically fails completely — around 68 degrees Fahrenheit — is not documented.

What is documented is the outcome.

She arrived at the hospital alive, however barely.

She was treated.

She recovered.

The Ongoing Mystery

Decades after the event, the precise explanation for Jean Hilliard’s survival remains somewhat incomplete.

The general framework is clear: severe hypothermia slows metabolism, reduces oxygen demand, and can preserve vital organ function at body temperatures and blood flow rates that would be lethal at normal temperature.