Unsolved Mysteries, which premiered in January 1987, captivated viewers with tales of peculiar cold cases, missing persons, and paranormal activity. Actor Robert Stack introduced reenacted segments—often while clad in a trench coat—and invited the audience to contribute tips and information to help law enforcement resolve their most baffling investigations. Thanks to their assistance, the series (later hosted by Dennis Farina) helped recapture numerous wanted fugitives, unite fractured families, and even exonerate a few wrongfully-convicted inmates.

However, many of the 1000-plus cases featured on the series are still awaiting resolution. We asked Unsolved co-creators John Cosgrove and Terry Dunn Meurer to share their picks for stories that have stuck with them over the years. In no particular order, here are 10 mysteries that still keep Cosgrove and Meurer up at night.

1. SALEM SECRETS (1989)

The Oregon state prison system didn’t have a great reputation in the 1980s. Allegations of employees smuggling drugs behind bars and stealing state property were rampant. To combat the perception of impropriety, then-Oregon governor Neil Goldschmidt invited Michael Francke to come in and clamp down on the activity as well as cure an overcrowding problem in facilities. Francke, who had previously worked within the New Mexico prison system, had a reputation for doing things by the book. He spent two years slowly building his case, but before he was able to point the finger at anyone publicly, he was found dead outside of his office in Salem on January 17, 1989—a victim of a knife-wielding assailant who had pierced his heart. Police pieced together Francke’s final moments and believed he was robbed and stabbed by a drug dealer named Frank Gable.

Although Gable was convicted, Francke’s family believed Michael’s death was related to his investigation into the prison system. One eyewitness said he saw multiple men running away from the crime scene on the night of his death, contradicting the Gable story. Oddly, no paperwork detailing Francke’s research was ever found—but several eyewitnesses saw employees carrying bags of shredded documents out of his office following his death.

Gable has thus far been unsuccessful in getting his appeals heard, despite several witnesses coming forward to cite police coercion during interviews and recanting their statements that he was at the crime scene. In 2016, a magistrate judge heard arguments for a new trial, including statements that deceased criminal John Crouse made to relatives in which he confessed to killing Francke in a car burglary gone wrong. Crouse revealed several key details of the crime, including the fact that he punched Francke in the face during the confrontation. Francke had a bruise on his face consistent with Crouse’s description. Though Gable is still considered the perpetrator, both Francke's family and the team at Unsolved Mysteries consider Francke's untimely death an open case.

2. A.W.O.L. (1993)

Soldiers who flee military enlistment without permission are known as being A.W.O.L.: Absent Without Official Leave. Private Justin Burgwinkel didn’t seem like a plausible candidate for stepping out on his responsibilities. He had worked hard and aspired to become an Army Ranger, which required specialized and intensive training at Ford Ord in Salinas, California; he seemed committed to a career in the military. And then he began acting oddly around his girlfriend, Iolanda Antunes. While visiting her, he would abruptly tell her he had to leave in order to meet unnamed parties. When she pressed for details, he told her it was a secret, hinting only that it might involve arms smuggling. She noticed he carried a briefcase full of shredded paper. Once, she answered the phone and was told to deliver Burgwinkel a message: “The mission” was being called off.

After three years in service, Burgwinkel simply vanished. His car was recovered at a motel three months after his disappearance, with all of his belongings—including his wallet, keys, and ID—inside. So were his military-issued dog tags, which he once told Antunes were useful in identifying the bodies of dead soldiers, adding "If you ever see these ... lying around, that means I’m dead." Some believe Burgwinkel suffered from a mental illness; others think he was involved in illicit activity that might have gotten him killed. No one has seen or heard from Burgwinkel since June 12, 1993.

3. DIAL H FOR ABDUCTION (1991)

Angela Hammond and her boyfriend Rob Shafer lived in Clinton, Missouri, and likely didn’t concern themselves much with the possibility of being victimized by the same types of crime that plagued larger cities. But on April 4, 1991, the worst-case scenario came true. While phoning Rob from a pay phone, 20-year-old Hammond remarked that a green Ford pick-up had been circling the block. Hammond said that a “filthy, bearded” man had exited and was using the phone next to hers. They talked for another few minutes—until Hammond screamed. Shafer raced to his car and drove to the phones, which were just blocks away. He told police he passed the pick-up driving away, with Hammond screaming his name. He tried to give chase, but his transmission failed, and he watched helplessly as the truck—which had a giant fish decal on the back window—disappeared into the night.

Shafer was initially considered a suspect, but was quickly cleared. Despite the telltale window sticker, police were unable to locate the vehicle or Hammond. They believed her disappearance might have been connected to two other women who were abducted and murdered within 100 miles of Clinton, but no one has ever been charged with the crimes.

4. DREAMY DISAPPEARANCE (1981)

Cynthia Anderson worked as legal secretary in Toledo, Ohio, sometimes passing the time in her office by reading suspense or romance novels. In 1980, the 20-year-old told her mother that she had been having a recurring dream about allowing someone into her house who meant her harm. At work, she received harassing phone calls to the point her employers—lawyers Jim Rabbit and Jay Feldstein—had an emergency buzzer installed at her desk. When Rabbit arrived at their office the morning of August 4, 1981, they expected to find Anderson behind her desk. Instead, the front door was locked, and Anderson was nowhere to be found. The novel she had been reading was open to a passage describing a violent abduction. Her car was still in the lot.

A month later, a mysterious phone call came into police headquarters. A woman insisted Anderson was being held in a basement but wouldn’t give any specifics. She called a second time to tell police the house was occupied, but never contacted them again. Some theorize Anderson may have heard incriminating conversations involving a drug dealer who became concerned that she knew too much. To date, no one has been charged in connection with her disappearance.

5. FRIENDS TO THE END (1987)

In 1980s Arkansas, a popular (albeit illegal) activity among youth was “spotlighting,” a practice in which a hunter would freeze animals in their tracks by shining a flashlight in their eyes while their partner fired a weapon. That’s what teenage friends Don Henry (16) and Kevin Ives (17) set out to do the evening of August 22, 1987 in the small town of Bryant, Arkansas, near the train tracks that ran behind Henry’s house.

Hours later, a conductor named Stephen Shroyer was navigating his train through the area when he noticed the teens laying motionless on the tracks; they were covered by a green tarp. Shocked, Shroyer tried to come to an emergency stop, but it was too late. The train ran directly over their bodies. A coroner would later conclude that the boys were asleep on the tracks as a result of smoking 20 or more marijuana cigarettes, a finding that both sets of parents rejected. Owing to public pressure, the bodies were exhumed so another autopsy could be conducted. The findings revealed that the boys had had one to three marijuana joints, and that one of them was dead and one unconscious before the train ran over them. That, coupled with the fact that Henry appeared to be stabbed and Ives struck with the butt of his own gun, led a grand jury to conclude the case was a double homicide.

In 2018, the Ives family was still pursuing answers with the help of a private investigator. In a bizarre twist, former professional wrestler Billy Jack Haynes claimed he was a witness in the case. He came forward to assert that, at the time, he was involved in drug trafficking in the area, and had been called to the area to make sure a scheduled air drop happened without incident. (In 1988, a confidential informant told police the area the boys were in was used to drop drugs from passing aircraft.) According to KATV, Haynes claimed he was present when an air-drop of cocaine took place and that the boys had witnessed the drop. Haynes also said he helped lay the boys on the track. Police have not yet commented on his claims.

6. TUPAC SHAKUR (1996)

Both Cosgrove and Meurer have been unable to shake the puzzling details that led up to the murder of 25-year-old rapper Tupac Shakur. On September 7, 1996, Shakur was in Las Vegas to watch Mike Tyson in a boxing match against Frank Bruno, and was riding with rap mogul Marion “Suge” Knight following the fight. Both men had run-ins with the law in their past and both flirted with danger in rap’s criminal element. Earlier that night, the two reportedly got into a physical altercation with members of the Crips street gang. Later, while driving, the men stopped at an intersection. A white Cadillac pulled up and opened fire. Knight was grazed by a bullet, but Shakur was hit four times—twice in the chest, once in the arm, and once in the thigh—and was in bad shape; he died of his wounds six days later. Of the many witnesses, only one came forward: Yafeu Fula, a backup singer for Shakur. Before he could try to identify any suspects or submit to further police questioning, Fula was gunned down at his home in New Jersey. No one has ever been arrested in connection with Shakur’s murder.

7. THE KECKSBURG UFO INCIDENT (1965)

Steven Spielberg couldn’t have scripted a better opening. On the evening of December 9, 1965, thousands of eyewitnesses reported seeing a strange light appearing over parts of the northeastern United States and Canada. Citizens of Kecksburg, Pennsylvania saw it, too, but they also witnessed a lot of commotion coming from what looked to be a crash site. Local law enforcement was said to have been quickly ordered out of the area by government officials who crowded around an acorn-shaped spacecraft embedded into the ground. Reports of the crash being a meteor or some kind of space debris circulated, but UFO researchers have long insisted the incident was extraterrestrial in origin. Others believe it was a spy satellite that the United States wanted to disavow. Neither NASA nor the Air Force has responded to civilian inquiries about what may or may not have landed in Kecksburg that night.

8. ONE MINUTE MILLION (1989)

On April 19, 1989, an armored car in Eden Prairie, Minnesota was besieged by a gang of armed robbers who quickly and efficiently relieved them of $1 million in roughly 60 seconds. While two stood guard with machine guns, a third put a (fake) bomb on the hood to encourage cooperation. The explosive rig was similar to one used in a robbery in Baltimore three years earlier. A year after the Eden Prairie heist, they struck a third time. In each case, no one was able to follow in pursuit, and the thieves were never caught. The FBI believed they were far from common criminals: Their protocol was so precise that authorities suspected they might have been heavily trained in ambush or attack scenarios, possibly as a result of entering the military.

9. ESCAPE FROM ALCATRAZ (1962)

Of the many notorious prison escapes of the 20th century, none proved as unbelievable as the three men who fled from the isolated Alcatraz, located on an island in San Francisco Bay, on June 11, 1962. Anyone who could successfully navigate past their cells, armed guards, and fences would then have to swim miles to shore. Inmates Frank Morris and Allen West hatched a plan to do exactly that, and enlisted brothers John and Clarence Anglin to come along with them. West had discovered that access to the outside was possible if the prisoners pulled out the entire ventilation shaft under the sink in their cells rather than trying to cut through the bars blocking the shaft. By burrowing into the opening, they could make their way behind the cell wall and up to the roof by using the plumbing to climb up.

After eight months of surreptitious digging, the men (minus West, who had trouble getting into the ventilation shaft) had created paths to the roof. They placed dummy heads—made from soap and concrete, plus hair swiped from the prison barber shop—in their beds so that guards wouldn’t notice they were gone. Once on the outside, they blew up a raft they had made from raincoats using a concertina, an instrument similar to an accordion. Then they vanished.

The next morning, their bunks were discovered to be empty, and authorities began a manhunt. The raft was found, along with some personal effects, but no bodies were ever recovered. The case was closed in 1979, but got renewed attention in early 2018 when it was revealed a man claiming to be John Anglin had written to the San Francisco police department in 2013 claiming to be alive but in need of medical attention for a cancer diagnosis. Handwriting analysis and DNA testing on the letter were inconclusive. If it’s genuine, then perhaps so is Anglin’s claim that both his brother and Frank Morris made it to shore alive, living decades as free men before Frank died in 2005, followed by his brother Clarence in 2008.

10. D.B. COOPER (1971)

Year after year, snippets of information continue to trickle out about “D.B. Cooper,” the alias for the man (or woman) who successfully hijacked a plane bound for Seattle on November 24, 1971. Cooper—who politely and calmly informed the stewardess that he had a bomb and demanded $200,000 in cash when the plane landed—got his money and jumped out of the aircraft with a parachute. Though traces of his ransom have been found and numerous people have told stories of people in their lives they suspect of being Cooper, authorities have never been able to nail down a single suspect. In 2018, an amateur sleuth and codebreaker named Rick Sherwood came forward to state that he had analyzed letters believed to be from Cooper and read the cryptography that indicated the criminal was identifying himself as Robert Rackstraw, a Vietnam veteran with parachuting experience. One letter hinted at three separate military units that Rackstraw belonged to. The FBI hasn’t made a specific comment on Sherwood’s claim. Neither has Rackstraw, who is still alive and was reportedly questioned by the FBI back in the 1970s.