PORTLAND, Ore. (KOIN) — December 7 will mark 60 years since a Portland family disappeared.

Ken and Barbara Martin, along with their three daughters — Barbara, 14, Virginia, 12, and 10-year-old Sue — drove to the Gorge in 1958. They were never seen or heard from again.

Greg Graven's grandfather Walter Graven was a detective in Multnomah County when the Martin family disappeared. (KOIN) 

“My grandfather was obsessed with this case,” said Greg Graven, whose grandfather, Walter Graven, was a Multnomah County detective at the time.

Greg grew up surrounded by the Martin case and his family saved his grandfather’s case notes. They clearly show Detective Graven was convinced of one thing.

“He believes that it was a homicide and it would be solved when the vehicle is located,” Greg said. 

The Martins left their home in the family’s 1954 Ford Station Wagon around 1 p.m. When they didn’t return, friends called the police, but no single agency took charge of the case.

After a few days, the Hood River Sheriff claimed the Martin’s car must have accidentally plunged into Cascade Locks while backing up in the parking lot.

The sheriff based his conclusion on some tire tracks and a credit card receipt showing Ken Martin had purchased gas in town.

Detective Graven kept investigating and to him, the Martin’s trip seemed odd.

“The time of day they chose to leave was not a common time,” Greg said. “Kenneth didn’t like to drive when it was dark outside.”

Witnesses reported seeing the Martins eating lunch at a cafe in Hood River. A waitress said the Martins left and headed toward The Dalles.

Detective Graven went there and discovered tire impressions on a bluff leading into the Columbia River. The tread matched the type of tires on the Martin’s car. 

Graven saw something else on a rock near the edge of the bluff.

“He also found paint chips were found that were sent to the FBI crime lab that were examined and were the same make, model and paint scheme of the Martin family vehicle,” Greg said. 

Then there was the gun found in Cascade Locks near an abandoned stolen car.

“It was completely coated with dried blood from whatever they had clubbed. They had clubbed something to death apparently,” Bonnie Cox said in 1986. 

Cox’s husband found the bloody gun and turned it over to the Hood River sheriff — but it was never processed as evidence.

Detective Graven connected the gun to the Martin’s older son, Donald.

An undated photo of Donald Martin in his Navy uniform. (KOIN file) 

Donald Martin was in the Navy and living back east. A few years earlier, he worked in sporting goods at the Meier and Frank department store, where he was accused of stealing that gun. 

“Walter Graven had definitely considered [Donald] if not a suspect, at least a person of interest,” said JB Fisher, who is writing a book about the Martin case. 

Fisher said Donald had a strained relationship with his family, something Detective Graven was aware of.

“He was very curious about what Donald Martin’s role might be,” Fisher said. 

Donald didn’t come back to Oregon during the search for his family, but Detective Graven interviewed him by phone.

Notes from Det. Walter Graven's investigation into the Martin family's disapperance. (KOIN) 

In his notes, Graven wrote: “It had to be planned out by — ” then a name is scratched out. His note continues to read, “no one else with a motive.” 

Using computer photo enhancement, Fisher determined the name scratched out is “Donald” — we don’t know exactly who or why the name was scratched out. We do know Graven’s bosses told him to leave the case alone. 

Frustrated, Graven wrote in his notebook, “Even though I can get no cooperation from anyone, there is no murder that can’t be solved.”

Then, in May 1959 — five months after the Martins disappeared, a barge hooked something below the bluff in The Dalles where Graven found the tire tracks and paint chips.

Two objects were seen floating up from the water. They were described as bundles of clothing.

Undated photos of the Martin family daughters, Barbara, Virginia and Susan. (File) 

A few days later, the bodies of Sue and Virginia Martin were recovered downriver. Although badly decomposed, the autopsy revealed a clue.

“The autopsy report says in describing the photographs that one of the photographs shows Virginia Martin with a hole in the head and that left a question there,” Fisher said. 

An undated photo of Detective Walter Graven. (file)

It was never clear what caused it. 

Donald Martin skipped the memorial service for his sisters, but did come back to Portland in June of that year to settle the family estate and meet with Det. Graven, telling him, “I know of no one who would murder my folks or no reason for it but I don’t see how it could have been an accident.”

Graven never was able to solve the Martin case and it haunted him for the rest of his life. Greg Graven followed in his grandfather’s footsteps and is now the chief of the Yamhill Police Department.

“This is my grandfather’s notebook and these are the words that I also heard him personally say in the past: “[this case] will be solved if I live long enough, for the car and bodies to be found.” 

Graven died in 1988 but his investigation lives on. He gave his notes to Jay Waterburry with The Dalles Police Department.

Walter Graven's notebook on his investigation into the Martin family's disappearance. (KOIN) 

“I would love to be able to see if we can get the car out and see if there’s any evidence or anything but as far as being prosecuted…I don’t know,” Waterburry said. 

For Dan Portwood with The Dalles PD, this is more than an unsolved case.

“I went to school with the two youngest Martin girls — with Susan and Virginia — and that was back in the ’50s when people just didn’t vanish,” Portwood said.

Can the Martin family mystery be solved 60 years after they disappeared? Detective Walter Graven’s words seem to reach from beyond, pushing for an answer.

“Grandpa is the last voice for the Martin family and he wants to be that last voice even still,” Greg said.

Watch: KOIN 6 News special documentary 50 years after the family’s disappearance