In February 1959, nine experienced Soviet hikers slashed open their tent from the inside and fled, half-dressed, into a night of lethal cold. More than sixty years later, science has an answer — but not everyone believes it.

A haunting elevator video, a body found in a rooftop water tank, and an official ruling of accidental drowning — yet the questions surrounding the Cecil Hotel have never gone away.

In 1922, six people were killed on a remote Bavarian farm — days after the farmer found footprints in the snow leading to his house but never away from it. A century later, Germany's most haunting cold case is still open in all but name.

In February 1978, five friends left a basketball game in California and were found months later, 70 miles off course on a frozen mountain — one of them had survived for weeks beside food he never touched.

In 1966, two Brazilian technicians were found dead on a hill near Rio de Janeiro, wearing suits, raincoats and lead masks over their eyes — beside a note about capsules and a signal that never came.

On a June night in 1912, an entire household in a small Iowa town was killed while sleeping. More than a century, two trials and countless theories later, no one has ever been convicted.

In 1994, nurses and doctors at a California hospital collapsed one after another while treating a dying woman. Three decades later, science still cannot fully explain what happened that night.

A GCHQ codebreaker was found padlocked inside a sports bag in his own bath. A coroner said he was probably killed. The police said he was probably alone. Both cannot be right.