On November 22, 1987, a figure in a Max Headroom mask broke into two Chicago TV signals in one night. The FCC and FBI investigated, but the culprits were never found. Here is what the evidence shows.

In July 1897 Salomon August Andrée, Nils Strindberg and Knut Frænkel set off by balloon for the North Pole and were never heard from again. Their last camp, diaries and film turned up on White Island in 1930. What killed them is still argued over.

In 1996 a pensioner in a Ural village near Kyshtym cared for a tiny being she called Alyoshenka. A police investigator filmed the witnesses, doctors disagreed about the body, and then it vanished. A 2004 DNA test pointed to a premature baby girl, yet the debate goes on.

Harry Houdini died in Detroit on October 31, 1926, days after a McGill student punched him in the stomach. Surgeons still debate whether a blow can trigger appendicitis, a 2006 poisoning theory found no physical evidence, and his widow’s Halloween séances ended in 1936 with no message.

For most of his life, the Key West artist Gene Otto kept a felt doll named Robert at his side. Today Robert receives letters of apology from strangers who blame him for their bad luck. How did a boy’s toy become the most feared doll in Florida?

On February 9, 1855, south Devon woke to lines of small hoof-shaped prints in the snow, and some locals blamed the Devil. Letters and sketches from 1855 show the marks varied in size, stride and place, which undercuts the legend of one creature walking 100 miles in a night.

In 1895 Michael Cleary told his Tipperary neighbors that the sick woman in his bed was a fairy changeling, not his wife. Days later she was dead. Did he truly believe the old stories, or did he use them to explain away a killing?

On December 9, 1965, a fireball crossed the sky and Kecksburg residents said something came down in the woods. An Air Force memo says searchers found nothing, and a NASA records lawsuit decades later turned up nothing on the case.