Two teens set off for a music festival. They were never seen again.

In the early hours of July 27, 1973, a teenager from Brooklyn, New York, set out to meet his girlfriend. The pair were planning to attend one of the biggest concerts in rock history, Summer Jam. 

The festival welcomed about 600,000 concertgoers, marking it as one of the largest gatherings of people in US history. Its founder felt "very, very lucky" nothing went awry.

After all, the rock fest was almost guaranteed to be a disaster, having only allocated for around 150,000 people. Teenagers snuck in through porta-potties, the local McDonald's was forced to airlift in more food, and the thousands of people who lined the fences put pressure on the venue to ultimately make it a free show. 

Historically, the event went off without a hitch — except for the strange disappearance of the two love-struck teens, who vanished on their way to the show. 

Now, Summer Jam is remembered not only for the music but also 16-year-old Mitchel Weiser and 15-year-old Bonnie Bickwit's disappearance. The pair, both gifted students, are the oldest missing-teen cases in America and were initially dismissed as classic romantic runaways expected to return home when their affection for one another ran out.

But 50 years on, the families of Bonnie and Mitchel are still dealing with the fallout from alleged police incompetence and a bungled investigation, along with the misfeasance of the New York City Police Department's Missing Persons Squad, which lost the original case file.

Ultimately, the mishandling impacted potential witnesses, investigative notes and dental records that could have led to the identification of any bodies.

 Bonnie Bickwit would be 65 today. Image: mitchelandbonnie.com.

There have been plenty of theories about what happened to the pair, along with false leads, and now a cold case that's officially been re-opened after years of loved ones' begging.

"A task force is exactly what we need to solve what happened to my brother Mitchel and his girlfriend Bonnie," Mitchel's sister Susan Weiser Liebegott told Rolling Stone. "Quite frankly, it is the only way to solve their case."

The couple were last seen leaving Cam Wel-Met – a popular summer camp in the Catskills region about 273 kilometres away from the festival, on the morning on July 27, 1973.

Bonnie, who would be 65 today, was a longtime camper and had taken a job at the camp as a parents' helper. Mitchel, who had stayed in Brooklyn, was working at a local photography studio.

A day before the pair were last seen by friends and family, Mitchel boarded a bus in Manhattan to meet Bonnie, about two hours away in Narrowsburg – about 250 kilometres from Watkins Glen, the town from which they'd planned to hitchhike the two hours it took to get to the rock fest.

His mother didn't want him to go, and Bonnie's ticket wasn't even hers.

"The original plan was for Mitch and I to go to Watkins Glen together, not Bonnie," Mitchel's high school friend Lady Marion recalled to Rolling Stone. "I purchased the pair of tickets."

Mitchel Weiser would be 66 today. Image: mitchelandbonnie.com.

The pair were determined to go, but Lady's mother understandably feared for his safety and forbade it. Mitchel's mother, Shirley, had pleaded with him not to attend — or, at the very least, to avoid hitchhiking. 

"I wanted to give him more money so he wouldn’t hitchhike," she said during a 1998 interview. "All he had was $25. But he ran out the door."

Of course, what happened next isn't known for sure.

On the case's 50th anniversary, Leemie Kahng-Sofer, who is the director of the Missing Children Division for the National Center for Missing and Exploited Children, said now is a perfect time to make a call to the public – specifically anyone who attended Summer Jam in 1973.

Perhaps an image, or a memory of Bonnie and Mitchel, who would be 66 today, could help uncover new information and lead to answers.

"The hope is that this is going to trigger a memory, a nugget of information that nobody was aware of before," they told Rolling Stone. "That could help break the case wide open."

Hope was renewd in June 2000, when a Missing Persons episode set its sight on Mitchel and Bonnie.

A crew was sent up to Camp Wel-Met, with journalist Eric J Greenberg and a psychic, who claimed they were dead and buried in the campgrounds, under a rock quarry.

"I believe that the murder took place up on the hill. Mitchel was murdered by a man who was a Vietnam War veteran. He then murdered Bonnie in another location several days later, I believe," the psychic said on Missing Persons.

The alleged perpetrator's name? "Wayne, Wade, or Willie, and... he is still alive."

A few months later, in October 2000, a then-51-year-old jewellery manufacturer worker named Allyn Smith stumbled upon the Missing Persons episode. After a lot of work to get into contact with a police investigator, he claimed he might know what happened to the teens, who he met while they were hitchhiking home. 

He said, according to Rolling Stone, that the couple could not get anywhere near the concert so had turned around. They looked young and "scrawny". 

The driver of an orange Volkswagen with Pennsylvania license plate picked all three of the hitchhikers up and, as it was hot, they stopped to cool off in the Susquehanna River (which is not far from Summer Jam) – a large body of water "known to sometimes have treacherous currents".

While Allyn stood at the water's edge, the teens went right in. It was then he heard the girl (thought to be Bonnie) screaming and saw her flailing in the water. The boy – thought to be Mitchel – allegedly went in to save her.

Both were swept away in the river and likely accidentally drowned, Allyn claimed.

According to reports, he thought it might be better off to not do anything. 

After all, they were in a secluded area, he didn't really know them and there was no one to call and nowhere to go for help. So instead of doing anything, Allyn and the driver returned to the van and left.

"[The driver] said, 'I'm going to be turning off to head for Pennsylvania soon. I'll call the police from a gas station,'" Allyn recalled in 2000, per Rolling Stone. "If he did [call], there might be a record."

He believed the driver would call the police, so Allyn never reported the incident. It didn't help he was high on marijuana.

But from this revelation, investigators had something to work with and tried desperately to corroborate his story. So Allyn went to New York, on his own dime, to help the investigation and with a detective, they combed every possible bridge to recollect footsteps. 

It was the big break the teens' loved ones and investigators had been waiting for. But unfortunately, no bodies were found. 

Because of the alleged drowning, it is assumed their bodies would have risen to the surface after days of building up gas. However, it is possible – although unlikely – their bodies were tangled underwater.

Because of how large Susquehanna is, the river stretches across about 64 counties, yet in 2000, only three county coroner's offices were checked.

There were other theories too, and a lot more work to be done on the Susquehanna theory to confirm its accuracy. What happened to the Volkswagen driver, and could the rest of the river be checked? Could Allyn be polygraphed to determine if his story was accurate? 

Before any further steps could be taken, two hijacked planes flew into the World Trade Center, killing almost 3,000 people. It triggered a national emergency and the main investigators dedicated to solving the case were reassigned.

It wasn't until 2013, 40 years after Mitchel and Bonnie went missing, that the case was revived with an unexpected phone call from a woman in Florida. She'd grown up not far from Watkins Glen and believed her father was involved in the murder. 

At the time, the woman (aged 51 when she reached out to police) was 11 years old and dining with her father at a restaurant when she approached a boy sitting at a table and asked him his name. She recalled him being uncomfortable and agitated. 

His name, she said, was Mitchel.

Her suspicions of her father were backed by years of sexual assault claims about him and other men, involving both herself and other children.

In October 2013, a neighbour – Sarah Saunders – was told her backyard would be dug up to look for evidence of bodies buried there. Interestingly, she'd recently consulted a psychic who'd asked if she had dead bodies around her house. Her town was also called Wayne – one of the suspect names given by the initial psychic who thought Mitchel and Bonnie were buried in Camp Wel-Met.

However, the excavations turned up nothing, and in its 50th year, the case remains unsolved. But while Bonnie's family do believe the pair died Susquehanna, Mitchel's loved ones have not given up hope.

The teens' parents have since died and Mitchel's sister is continuing the fight to find out just what happened to the pair.

Feature Image: mitchandbonnie.com.