In December 1946 an 18-year-old student walked up a Vermont mountain trail in daylight, was seen by several people, and vanished. Hundreds searched. They found nothing at all.

The biggest manhunt Britain had ever mounted spent 18 months chasing a man who did not exist. It took 26 years and a scrap of dried envelope glue to find out who invented him.

In 1992 Rachel Nickell was killed in broad daylight on a London common while her 2-year-old son watched. For 16 years the police chased the wrong man - while the real killer was already in their files.

Something destroyed 4 square km of a walled capital in a single instant and was heard 150 km away. 400 years later, historians still cannot say what it was.

A cargo ship found a small racing yacht drifting with nobody aboard, and 3 logbooks on the table that explained everything except the one thing that mattered.

Several hundred slabs carrying the same strange message are pressed into the roads of two continents. The method is understood. The hand behind it is not.

500 children arrived for a marching band competition. Within hours, 259 people were in hospital and nobody could say why. Forty-six years later the official file still blames fear, and the babies who collapsed have never been explained.

The Inca ran an empire of millions without writing a single letter. They used knotted cords instead. We cracked the numbers a century ago, and everything else on those cords has resisted us ever since.

A 222 metre ship with 29 men aboard vanished from another vessel's radar in a November storm. There was no distress call and no survivor. Fifty years and two official inquiries later, nobody agrees on what sank her.

The same female DNA turned up at 40 crime scenes in three countries, including the murder of a young policewoman. Hundreds of officers hunted her for years. Then one impossible test result revealed where she had really come from.

A police constable signed a statement saying she watched a chair slide across a council house floor with nobody near it. What followed was the most heavily recorded haunting in British history, and the most heavily disputed.

A man calling himself R.C. Christian walked into a Georgia granite yard in 1979, ordered a 108 tonne monument in eight languages, and vanished. In 2022 somebody blew it up. Both men are still unidentified.