COTTONWOOD, Ariz. — In this episode of Arizona's Hardest Cases, we take a look at a cold case investigated by the Yavapai County Sheriff's Office. Hear how they were able to track down a murder suspect and get him to confess 15 years later. ABC15 also obtained exclusive audio from some of the interviews with detectives.

Crystal Forrest, 64, was first reported missing in March 2009. She met convicted murderer Robert Reed at the DCS office in Cottonwood. Sheriff's office officials say Forrest had befriended Reed and was trying to help him get back on his feet, but her employer, who was giving her a place to stay, wasn't sold on the idea.

This story is part of ABC15's regular Coldest Cases series. Watch this entire episode of Arizona's Cases now on your Roku, Fire Stick, or other streaming device. Part 1 of the episode can be viewed in the player below.

Part 1: Arizona's Most Unsolved Case: A Look at How the Yavapai County Sheriff's Office Solved the Crystal Forest Murders

Forrest loved traveling the world, so she decided to move that night, and asked Reed to help her drive her to Austin, Texas, to drop off her belongings, then fly to Mexico and stay with a friend.

Investigators determined the pair made it to El Paso, but the trip ended there and Forrest was never seen or heard from again.

Forrest rented a U-Haul to help with the move. Detectives say the vehicle was returned to Las Cruces, New Mexico a few days later. During the investigation, detectives discovered that Reed had been on the run, using the identity of a former roommate. A search of his real name revealed an outstanding warrant for his arrest in connection with the arson incident. Reed was arrested on the warrant a month later and sentenced to 18 years in the Arizona Department of Corrections.

Detectives tracked down Reed and questioned him about his relationship with Forrest. Reed explained that he met Forrest in a Walmart parking lot in Cottonwood to try to buy her a car. Sheriff's Office deputies said things were suspicious and that his story has become more detailed since then.

Investigators continued to question Forrest over the years while he was in prison, and detectives pointed to other crimes he had committed and future charges he might face, using them to elicit answers.

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“Again, I don't know if you're telling me anything … I understand why you don't want to get found out, but my concern, my personal concern is for Crystal Forrest,” Detective Brown with the Yavapai County Sheriff's Office said.

“I don't know anything about Crystal other than, like I said, I bought a truck from her and I worked for her for one day,” Reid replied.

Reed eventually confessed to killing Forrest in 2014 and used Google Earth to show detectives the exact location of his body, which was along Interstate 10 in rural El Paso. Reed claimed he had been in an argument with Forrest and shoved him, causing him to fall and hit his head.

Sheriff's office officials said Reed died in prison several years ago.