Off and on between 1987 and 1999, Robert Stack creeped out people all over America as the deep-voiced host of Unsolved Mysteries, a true-crime series designed to solve cold cases and unexplained paranormal phenomena by sharing stories with wider audiences. From serial killers to alien abductions to missing persons, Unsolved Mysteries showcased hundreds and hundreds of stories about eerie, sometimes deadly, occurrences. Viewers breathed a sigh of relief when an update at the end of a segment explained the criminals were apprehended or the missing people were found.

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Unfortunately, many of the cases highlighted on the show remain unsolved, even decades after airing on national television. Some of the cases date back to the 19th century, while others are still being investigated to this day. This list looks into 10 such unsolved cases that aired on Unsolved Mysteries during its television run.

The Disappearance Of Glen And Bessie Hyde

The Hydes were young newlyweds who vanished while traversing the rough waters of the Colorado River, which travels through the Grand Canyon, in 1928. Glen, seven years Bessie's senior, was an experienced river runner who'd completed similar expeditions on the Salmon and Snake Rivers in Idaho.

After visiting with their friend on the canyon's South Rim, photographer Emery Kolb, on November 18, they were never heard from again. Their abandoned boat was found on December 19, and their bodies were never recovered. Theories abound about what happened, including one that Bessie murdered Glen and then assumed a new identity.

The Cash-Landrum Incident

Near the end of 1980, two older women and a 7-year-old boy driving together in Southeast Texas spotted an unidentified flying object in the sky. The diamond-shaped object emitted a bright light that followed them, and they eventually pulled the vehicle over to examine the UFO. The object's lights were so intense that it caused the metal on their vehicle to become hot to the touch.

The trio then watched the UFO soar into the sky, followed by nearly two dozen military helicopters; when they got home that night, all three experienced nausea and headaches. A local police officer later claimed to have seen a similar sight in the sky that night, but the U.S. military has discredited all the witness testimony.

Connecticut River Valley Killer

This still-unidentified killer is responsible for at least seven deaths in and around Claremont, New Hampshire, and the corresponding Connecticut River Valley between the late 1970s and late 1980s. The victims were all women who were brutally stabbed dozens of times.

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One woman, who was pregnant at the time, survived the attack, despite receiving 27 wounds. She described her assailant as a male in a Jeep Waggoner, and she was even able to provide police with a composite sketch and the first three characters of his license plate. Despite this information, the man was never apprehended, and the murders stopped after the incident.

Baron 52

A week after the Paris Peace Accords officially brought an end to the U.S. involvement in the Vietnam War, an Air Force EC-47 plane with the call sign Baron 52 was shot down over Laos. There were eight crew members on board, yet only the remains of four were found among the plane's wreckage.

While the U.S. military considers the other four killed in action, the family members of the men and POW/MIA advocacy groups believe the men survived. While none of them have ever been located, some people close to the case suspect the men were kidnapped by the Soviet Union, who maintained a strong presence in both Laos and Vietnam after the war ended.

The Death Of Bobby Fuller

Bobby Fuller was a rock star who died under mysterious circumstances at the height of his career. With his group The Bobby Fuller Four, he produced hit singles like "Let Her Dance" and "I Fought The Law." When he was only 23, Fuller was found dead in his car, which was parked outside his Hollywood apartment. The year was 1966.

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Fuller's remains lacked signs of beatings or bruisings, but the upper parts of his body were covered in hemorrhages caused by gasoline vapors and summer heat. Both boxes for "accident" and "suicide" were checked on the coroner's report, but each was followed by a question mark. Some still suspect foul play, one former bandmate going as far as blaming Charles Manson's crew.

1995 Palo Verde Derailment

On October 9, 1995, Amtrak's Sunset Limited train derailed while passing through Palo Verde, Arizona, on the Southern Pacific Railroad tracks. Four of the eight derailed cars fell 30 feet below off a trestle bridge into a dry river bed. Seventy-eight people were injured, twelve of them gravely, and one sleeping car attendant died.

Upon investigation, police discovered the rails had been intentionally shifted out of position and reconnected with wires, bypassing security systems designed to warn train conductors about track problems. Officials believe someone with knowledge of railway systems was responsible for the tampering, but no one was ever apprehended.

Mad Butcher of Kingsbury Run

In the 1930s, a serial killer of Jack the Ripper's caliber terrorized residents of Cleveland, Ohio's Kingsbury Run. A dozen victims found between 1935 and 1938, most of whom were working-class, were horrifically tortured and dismembered. Police believed poor drifters and laborers, desperate for income, were easy targets for the killer.

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At the time, famous Prohibition Officer Eliot Ness was the Public Safety Director of Cleveland. Despite the media scrutiny and heinous nature of the murders, no one was ever charged with the crimes. The murders were eventually connected to similar slayings in nearby states, but that did not yield a culprit.

Allagash Abductions

Four men who were on a camping trip in Maine on August 20, 1976, later claimed to have been abducted by aliens after sighting a UFO. The men received hypnotic regression therapy, during which they shared details about being probed and tested by four-fingered extraterrestrials.

After the friends received plenty of media coverage about their claim, one of them, Charles Rak, changed his narrative. Rak claimed that while they did see strange lights and objects in the sky, they were not beamed up by aliens. The other men still stand by their story.

Mary Celeste

The merchant brigantine Mary Celeste was found floating adrift off the coast of Portugal on December 4, 1972. A Canadian vessel came upon the American ship, which was under partial sail and lacking its lifeboat. The ship's last log entry was dated ten days earlier, and it was on its way to Genoa from New York with a cargo of denatured alcohol.

The cargo was found intact, yet every crew member was missing. None of them were ever heard from again, and numerous theories exist about their whereabouts, ranging from waterspouts to giant squids.

Interstate 70 Killer

In 1992, an unknown male went on a killing spree along Interstate 70 in the Midwest. He killed six store clerks whose places of business were close to the interstate. Five of them were petite brunette women, and one of them was a male with long, dark hair believed to be mistaken for a woman.

Each of the stores was robbed, but robbery is believed to be a secondary motive. They were all shot at close range. The murders match other killings in Texas that occurred in 1993 and 1994, yet no one has been charged for any of the crimes.

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