1. The Toynbee Tiles

The Toynbee Tiles are a series of mysterious messages found embedded in asphalt around various cities in the United States. While it is unknown exactly where or when they started showing up, they were first mentioned in the media in 1994, in The Baltimore Sun. Their messages are strange and seemingly nonsensical. Many of the tiles contain variations of the message "TOYNBEE IDEA IN MOVIE '2001 RESURRECT DEAD ON PLANET JUPITER." While multiple theories have been put forth about who has been installing them or what they mean, nobody has ever figured who created them or why.

2. The Disappearance of Madeleine McCann

Madeleine McCann was a three-year-old British girl who disappeared while on holiday with her family in Portugal. One night, her parents left Madeleine and her siblings asleep in their apartment while they were dining with friends at a nearby restaurant, checking on the children throughout the evening. At one point in the night, Madeleine's mother went to check on them, and discovered that Madeleine was missing. What ensued was an investigation that was not only horribly botched by the Portugese police, but led to the McCann's being accused of murdering their own daughter.

While the case has never been solved, many theories have been put forth, including that a local kidnapped Madeleine and raised her as his own, or that the McCann's accidentally gave Madeleine an overdose of sleeping medication and hid her body out of fear.

3. The Murder of Missy Bevers

In 2016, 45-year-old fitness instructor Missy Bevers was murdered inside Creekside Church in Midlothian, in the early morning. She had been preparing to teach a class at 5 am. The cause of death was puncture wounds to the head and chest. Police discovered surveillance footage of the suspect wandering the church in full tactical gear (you can watch it here if you don't value your sleep), holding a hammer that was presumably used to kill Missy.

One strange aspect of the footage is that the suspect is shown to have an unnatural posture when walking. Police could not determine whether this was intentional or due to some kind of disability or injury. Though police believe the attacker to be male, Missy's husband believes that the attacker was female and that the murder was committed out of some kind of personal grievance. Police investigations also revealed that Missy had financial troubles and was unfaithful in her marriage, but they could not establish a motive for her brutal murder.

To make things even stranger, Missy's father-in-law was reported to have brought a women's shirt covered in blood to the dry cleaner's, claiming his dog had been injured and gotten blood on it. The cleaners reported it to the police, and it was subjected to DNA testing. While it was ruled out, it was determined that Missy's father-in-law is roughly the same height and build of the attacker, and he remained a person of interest in the case.

The case is still unsolved to this day.

4. The Disappearance of Asha Degree

Asha Degree was a nine-year-old girl living in Shelby, North Carolina, who disappeared under mysterious circumstances on February 14, 2000. Coming from a close-knit family, she lived with her brother and parents, who did not allow a computer in their house specifically out of fear of internet predators. Asha was known to be shy around adults and scared of the dark, which makes what occurred on February 14 so strange.

In the early morning, while it was still dark and there was heavy winds and rain, a truck driver and motorist spotted Asha walking along the highway with a small backpack. The motorist turned his car around, concerned to see such a small child walking by herself at that hour, but then Asha ran into the woods and disappeared.

Her parents discovered she was missing later in the morning, and an extensive search quickly commenced. No evidence of her was found until a year and a half later, when her backpack was unearthed near the same highway she had been walking along.

While the circumstances suggest she had been running away, Asha was much younger than children who usually run away, and police could not find a motive for why she would do so when there was no evidence of abuse or dysfunction in her family. While the consensus seems to be that she was lured away by a predator, nobody has a solid theory of how somebody was able to lure such a quiet and cautious child away when her parents took extensive lengths to protect her and did not allow internet use in their house.

To this day, no further evidence of Asha's fate has been found.

5. The Dancing Plague of 1518

In Strasbourg, Alsace, of the Holy Roman Empire in 1518, around 400 people started dancing erratically, without rest for over a month, with some collapsing or even dying.

It began on July 15, when a woman, Mrs. Troffea, started dancing in the streets. This lasted for about four to six days. 34 others joined within a week, and within a month there were 400. Interestingly, most of them were reported to be women. City authorities tried to contain the situation, but to no avail. While city officials did not list the number of deaths, there is ample historical evidence to prove that this did in fact occur.

To this day, nobody knows exactly what caused the bizarre behavior, though it is theorized that it may have been caused by an outbreak of ergot poisoning, though this has since been discredited. Most simply chalk it up to mass hysteria egged on by superstition and rampant starvation in the area, making the victims more susceptible to irrational thinking and behavior.