How Mother of a Missing Teen Helped Bring America's Oldest Suspected Serial Killer to Justice

Annette Craver loved adventure.

At age 15, the poetry-writing singer and songwriter fell in love with a handsome stranger in his early 40s, Felix Vail, who showed up at a Houston yard sale on his motorcycle. They took off traveling after her graduation, and they married when she was 17.

But the next year, 1984, Craver vanished – and with a dubious explanation from her new husband.

"I had a suspicion immediately," Craver's mother, Mary Rose, tells PEOPLE in this week's issue, on newsstands now.

Her intuition questioned Vail's claim that he'd put Craver alone on a bus bound for Mexico. But it's what she learned years later that pushed Rose even harder: Vail was suspected in the 1962 death of his first wife, Mary Horton Vail; and another mother had been searching for a daughter, Sharon Hensley, last seen with Felix and who went missing in 1973.

After connecting those families – and enlisting Jerry Mitchell, a Clarion-Ledger/USA Today investigative reporter in Felix's native Mississippi, whose digging added new revelations that fueled a 2013 homicide charge against him for Mary's death – Rose was in court in August when Felix, a 77-year-old suspected serial killer, was found guilty of killing Mary almost 54 years ago.

On Monday, Felix, who maintains his innocence, was sentenced to life in prison for that murder, reports The Clarion-Ledger. His attorney, Andrew Casanave, told PEOPLE he plans to appeal.

For much more on the mysteries surrounding Felix Vail, and a timeline of deadly revelations surrounding his case, pick up this week's issue of PEOPLE, on newsstands now.

The verdict brought Mary's death full circle for her family, after decades in which they doubted Felix's story that the 22-year-old fell from a boat and drowned on the Calcasieu River near Lake Charles, Louisiana, on Oct. 28, 1962.

Felix was questioned but never charged, despite the coroner's findings of bruises on Mary's head and neck and a scarf in her mouth. It also emerged that Felix had taken out a double-indemnity insurance policy on his new bride.

Prosecutors used Craver and Hensley's subsequent disappearances to strengthen their circumstantial case against Felix. But the other families still don't know what became of their girls and concede they may never know.

"I'm feeling like I just need to be at peace with the knowledge that he is a killer and that Annette is gone," says Craver's mother, Rose, a retired social worker. "When the verdict was read, I felt that justice had been done for all three women."

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A Mother's Intuition

Although Felix faces no other charges, the disappearances of Craver and Hensley were invoked during his trial, and he was prosecuted as perhaps the nation's oldest suspected serial killer.

"We have long since surpassed the possibility that these are all just coincidences," Calcasieu Parish District Attorney John DeRosier tells PEOPLE.

The families of Mary and Hensley credit Rose for helping to prod the look at Felix's past.

"Jerry Mitchell made all the difference in the world," Mary's brother, Will, tells PEOPLE, applauding the journalist who took the leads Rose provided and chased them down. "But without Mary, none of this would have happened."

Says Mitchell: "Mary Rose never tired, never stopped, never gave up."

Rose, 68, last saw Craver in the spring of 1984. By then her daughter's short marriage to Felix was crumbling. While married to Felix, Craver had come into a $100,000 inheritance, and soon after she signed over property to Felix that she previously had shared with her mother.

"He really manipulated her mind," Rose says.

Before she turned 19 that fall, Craver was gone. Felix later said she had a dream about Mexico, and he put her on a Trailways bus headed south of the border.

Her mother never heard from her again.

Rose hired private investigators who produced little. Then, on a whim years later, she showed up at the doorstep of Felix's sister.

"She let me in, and we talked, and she talked," Rose says.

'I Could See the Pattern'

When the sister casually said Felix's first wife supposedly drowned and the insurance company had questioned it, "my ears perked up," says Rose. Then, she says, the sister recalled another woman who had been calling Felix's mom looking for her missing daughter.

She knew the second woman's name was Sharon.

"It put my investigation into motion," Rose says. "I could see the pattern. Even before I spoke with those other two families and got more information, I said, 'This man is a killer.' "

She located the Horton family in Louisiana from newspaper clippings. "She said, 'You don't know me, but my daughter married Felix Vail and she's missing,' " Will Horton recalls of their meeting.

He says he had no idea about the other two women. But a Horton family member had kept an article with this detail: Before she died, Mary and Felix had a son, Bill, who went on to live with his father and Sharon Hensley in California.

At one point Bill had told California police he allegedly overheard his father confess to Mary's murder, according to the Clarion-Ledger. (Bill died in 2009 of cancer.)

That connection led Rose to the Hensley family in North Dakota. The story they told sounded familiar: Felix told them Hensley, whom he called his wife, had abruptly decided to leave him and travel after meeting a couple who invited her to join them on a sailing trip. She, too, was never heard from again.

At his sentencing, Felix repeated his stance that Mary's death was an accident and that Craver and Hensley "chose to disappear themselves from abusive mothers."

Rose viewed it differently.

Finding Allies

"She called and asked me, 'Would you be interested in a story about a serial killer living in Mississippi?' " recalls Mitchell, the journalist, who first met with Rose in mid-2012 – then with Will, and then with the district attorney in the Louisiana parish where Mary had died.

"That's the first I'd ever heard of this incident," says DeRosier, whose review of Mary's death, aided by friends of Felix's who said he'd confessed his role to them, led to Felix's 2013 arrest and the guilty verdict.

"The more I heard about the story, the more interesting I found it," DeRosier tells PEOPLE, "particularly when you started adding in the disappearance of the other two ladies."

Says Rose: "I was determined that I was going to advocate for all three of these women."

Of the bonds she has since formed with Will and Hensley's brother, Brian, through years of investigation, arrest, trial and conviction, Rose adds: "In tragedy, they have become my brothers.

"I've never had this kind of a bond before. We've had his tremendous loss. Sharon and Mary were their only sisters. And of course, Annette was my only child."

"I know that I haven't fully grieved," Rose says of the questions that still surround her own daughter's loss. "If we found a bone that matched her DNA – just even saying that makes me feel like crying."

"I don't want to make that my next goal," she says. "I can only pray that he [Felix] wants to come clean. But I don't feel hopeful at this point that he will."