A mother's 13-year journey for justice and an exclusive look at the FBI investigation that solved her daughter's murder

In April 2009, Brittanee Drexel told her mother she would be spending a few days at a friend's house in Rochester, New York. But what Dawn Drexel didn't know was that her 17-year-old daughter was really more than 800 miles away on a spring break trip in Myrtle Beach, South Carolina, without permission.

Brittanee was last seen exiting a Myrtle Beach hotel lobby.

It was a case that kept the Drexel family on edge for 13 years and kept the nation in suspense as investigators searched long and hard for the high school junior.

A new "20/20" episode airing March 8 at 9 p.m. ET and streaming on Hulu the next day takes a behind-the-scenes look at the FBI investigation to solve Brittanee's murder and the arrest and plea deal that brought justice to the family.

The show features exclusive interviews with key members of the FBI investigative team and never-before-heard details of how they cracked the case.

Dawn Drexel had no idea that Brittanee had snuck down to Myrtle Beach until she heard from her boyfriend, John, a few days later.

John did not travel with Brittanee to Myrtle Beach, but kept in constant contact with her, text messaging his girlfriend during her trip until their text message exchanges abruptly stopped on April 25, according to police records.

Investigators said they tracked Brittanee Drexel's cell phone pings from Myrtle Beach to a rural, swampy area nearly 50 miles south.

Despite searching the dense and desolate Lowcountry swamp on horseback, ATV and foot, investigators came up empty.

Investigators eyed Raymond Moody, a registered convicted sex offender they identified through the local sex offender registry, who was living 10 miles away from the last place Brittanee’s phone pinged.

Moody had returned to his hometown of Georgetown, South Carolina, after being convicted and serving approximately half of his 40-year sentence in California for multiple sexual assaults.

In 2011, investigators conducted a search of the motel in Georgetown, where Moody had been staying at the time of Brittanee Drexel’s disappearance.

But the search of the motel produced no evidence that could connect Moody to Brittanee.

Still, more than ten years would pass before significant new information would help investigators discover what happened to Brittanee and who was responsible for her disappearance.

By that point, a new FBI team had stepped in and started re-examining the evidence, including Drexel's cell phone location pings and surveillance footage from the boulevard in Myrtle Beach where Brittanee had been walking the night she vanished.

Caleb Messer, an FBI intelligence analyst, told "20/20" in an exclusive interview that "eventually there was a point in time where there was one specific vehicle that stood out to us." That vehicle was a 1998 Ford Explorer.

Investigators found documentation that a woman named Angel Vause, Raymond Moody’s girlfriend, had had access to that same vehicle.

Authorities interviewed Vause after discovering a police recording where she was documented on tape while talking with a friend, saying that she was responsible for Brittanee Drexel’s death.

Investigators could not corroborate her claim, but saw an opportunity to try to get to Moody, whom they suspected was actually responsible.

During the interview, Vause claimed she had been drinking the night of the recording and that her friend kept asking about Moody. She said that she was just trying to get the attention off him.

"I just wanted everybody to leave him alone, so I put the blame on me instead of him," she told investigators, admitting that her claim to be responsible wasn’t true.

Vause told the FBI she still possessed the cell phone that she had at the time of Drexel's disappearance and offered to locate it for them, but after leaving her interview, she never followed through.

Investigators then decided to execute a search warrant for that phone and wound up face-to-face with Moody.

"I give Ray a copy of the search warrant, he can put two and two together and start to realize that we've got evidence and, ultimately, we would go after whatever and whomever we had to, to get justice for Brittanee Drexel," Hank Carrison, a senior investigator with the Georgetown County Sheriff's Office, told ABC News.

Soon after, Moody’s lawyer contacted the local prosecutor, Fifteenth Circuit Solicitor Jimmy Richardson, and asked to meet. In May 2022, Raymond Moody confessed to picking up Drexel in the Ford Explorer, then raping and strangling her.

Moody told investigators he was driving with Vause when they picked up Drexel on the Myrtle Beach strip and went to a remote boat landing south of Georgetown.

He said Vause had no involvement in her murder. He said that during a period of time when Vause had left and he was alone with Drexel that night, he raped and killed the 17-year-old.

He then took investigators to a wooded area where he claimed he buried the body while Vause was sleeping.

After three days of excavating, investigators found human remains on May 11. Forty-eight hours later, Brittanee Drexel’s remains were positively identified through her dental records.

Moody was charged with obstructing justice, kidnapping, criminal sexual conduct and murder.

Dawn Drexel told "20/20" she was shocked when she learned that Moody was in custody.

"I go, 'You've got to be kidding me,'" she said, recalling that Moody had been identified as a person of interest in 2011.

Vause also gave a proffer statement to investigators about the night’s events. Under its terms, she agreed to fully tell the truth while the state agreed to take her cooperation into account in deciding whether to prosecute her.

Vause admitted that she was in the car when they picked Drexel up, and said that she was still alive when Vause left her and Moody at the boat landing. Vause said that when she returned, Drexel was gone and that Moody told her a friend had come and picked the girl up.

According to prosecutors, phone records show that there was a time during that night when Vause and Ray were not together.

Vause was not charged in connection with Brittanee's disappearance.

On Oct. 19, 2022, Moody pleaded guilty to murder, kidnapping and criminal sexual conduct in the first degree. The state dropped the obstruction of justice charge.

"Once he walked into that courtroom, I was so angry," Dawn Drexel said.

"He wouldn't even look at me, and I was shaking. I was that mad," she added.

Moody was sentenced to life in prison without parole, in addition to two consecutive terms of 30 years.

At a memorial for Brittanee in 2022, Dawn Drexel recognized the FBI team that cracked the case and presented them with a pendant. It had a picture of Brittanee on one side and the message "Thank you for finding me" on the other.

"There is nobody more singularly responsible for the resolution of this case than Dawn Drexel," FBI Special Agent Michael Connelly said.