At bedtime on the night of February 23, 2005, Jessica Lunsford slipped under the covers – wearing a pink nightgown and clutching her stuffed purple dolphin under her arm – and fell asleep.

Jessica was never seen alive again.

The 9-year-old girl disappeared in the middle of the night from the Homosassa, Fla., home where she had lived for a year with her father, Mark Lunsford, then 41, and her grandparents.

Authorities searched for the third-grader for nearly a month before finding her body in a shallow grave, wrapped in a plastic bag, just 150 yards from her home.

Her heartbreaking crime is the focus of the season premiere People magazine investigates Monday, October 28.

Airing on Investigation Discovery/ID at 9/8c and airing on Max, the episode, titled “The Boogeyman,” details what happened that night, the exhaustive search for Jessica — and how authorities finally caught her sadistic killer.

Monday nights feature back-to-back episodes, with “A Story to Die For,” about the murder of reporter Sarah Greenhalgh, following the episode about Jessica’s murder, airing Monday, October 28 at 10/9c.

In the days following Jessica’s disappearance, search and rescue teams scoured Citrus County for any sign of the little girl.

On March 5, police suspended search and rescue efforts to focus resources on following up on phone tips and other key leads.

During their investigation, they learned of a man named John Couey, then 46, who was staying in a mobile home across the street from the Lunsfords when Jessica disappeared.

In an exclusive clip from the episode, retired Citrus County Sheriff Jeffrey Dawsey talks about how they started closing in on Couey as a suspect.

“One of the individuals came from Maddie Secord, Couey’s niece,” Dawsey says.

“Maddie Secord came forward because she knew John Couey’s history of sexually assaulting people. She told us that Couey lived in the house across the street from Jessica Lunsford, but no one knew that.

The house belonged to Dorothy Dixon, Couey’s sister, who was one of the people interviewed by police when they began canvassing the neighborhood. But when the police went to her house, they were only allowed in certain parts of the house — something that seemed worrisome after learning about Couey’s past.

“We walked right into this house and maybe the baby was there and we missed her?” says Dawsey.

On March 17, 2005, police arrested Couey, who slipped into the Lunsfords’ home through the unlocked front door, put his hand over Jessica’s mouth and led her to the trailer where she had been staying.

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Authorities don’t know how long Jessica lived after she was kidnapped, but they say he raped her before burying her alive.

He was a convicted sex offender who failed to register his new address, which was required by law, authorities said.

He was convicted of Jessica’s murder in March 2007 and sentenced to death.

He died in 2009 of natural causes.

People Magazine Investigates: The Boogeymanseason premiere, airs Monday, October 28 at 9/8c on Investigation Discovery/ID and airs on Max. This episode is immediately followed by another People magazine investigates episode, “A Story to Die For,” about the murder of reporter Sarah Greenhalgh, airs at 10/9 c.

If you or someone you know has been sexually assaulted, please contact the National Sexual Assault Hotline at 1-800-656-HOPE (4673) or go to rainn.org.