Two Virginia Tech students are charged in the death of a seventh grade girl. Here is what you need to know about the investigation. (Claritza Jimenez/The Washington Post)

— Nicole Lovell slipped out her bedroom window on a cold January night, seeking the promise of a romantic walk in the woods. The 13-year-old grabbed her cellphone and her “Minions” blanket, nurturing a dream of running away with the trim Virginia Tech athlete she had met online.

The secret rendezvous with freshman David Eisenhauer was a ruse, police testified Friday, part of an elaborate plan he hatched with a close friend to kill the middle school student and keep his inappropriate relationship with her from becoming public. His friend Natalie Keepers also had a sinister motivation, a police detective testified, recounting how Keepers told police that she was a “sociopath-in-training” and that the secrecy and intrigue surrounding the murder plot gave her “the best feeling.”

Along a dark country road, in a swath of woods Eisenhauer and Keepers had scouted for the crime, police said, Eisenhauer stabbed the girl to death, blood staining the snow.

Detectives testified in a preliminary hearing Friday that the two Virginia Tech students believed they had planned a perfect crime. They shut off their cellphones; they hid the knife in the woods; they tossed Nicole’s belongings in a dumpster and a raging river; and they bathed her body with cleaning wipes before dumping it in North Carolina.

And they believed they would get away with it. Police said that Eisenhauer told Keepers that thousands of children go missing every year and are never found.

Nicole Madison Lovell, 13, was slain in January. (Deana Jones/Blacksburg Police Department)

“It will never be traced,” Eisenhauer said in a text message to Keepers, according to police. “Always go overkill when your life is on the line.”

Detectives testified for three hours Friday, detailing how the pair plotted to end Nicole’s life and conceal the crime. Despite a belief that the slaying wouldn’t be traced to them, police said, a series of missteps was their undoing: A GPS device in Eisenhauer’s Lexus remained on, tracking the car’s movements that night; Nicole’s blood seeped into the car’s trunk; and the two students later exchanged incriminating text messages.

Keepers, who broke down during an interview with police after Nicole disappeared, ultimately recounted to detectives how the crime unfolded and turned over her cellphone, police testified.

Eisenhauer, 19, of Columbia, Md., is charged with abduction and first-degree murder in Nicole’s death. Keepers, 19, of Laurel, Md., is charged with accessory before the fact and concealing the body. Mary Pettitt, commonwealth’s attorney in Montgomery County, Va., said Keepers helped Eisenhauer plan the killing and then helped try to cover it up.

A judge determined Friday that there is enough evidence to move the case against each student to a grand jury, which is scheduled to meet July 26. Pettitt dropped a misdemeanor charge of accessory after the fact against Keepers.

Attorneys for Keepers and Eisenhauer declined to comment.

The investigation began Jan. 27, when Nicole’s mother, Tammy Weeks, reported the 13-year-old missing after going to the girl’s bedroom and finding a nightstand shoved up against her door to prevent entry. Her disappearance set off an intensive search that ended three days later, when her body was discovered.

The slaying shocked the Blacksburg community and raised concerns about the dangers teens face when they interact with strangers online.

Nicole’s mother said her daughter was the target of bullying at Blacksburg Middle School, had grappled with health problems and frequently poured her sadness out online, where she sought solace and drew the attention of young men. Authorities said that was where the vulnerable teen encountered Eisenhauer, then 18.

Eisenhauer walked into the courtroom Friday wearing a black suit, blue tie and a blank stare. Keepers, in a pink hooded sweatshirt and a dark skirt, kept her head bowed.

Nicole’s mother stormed out of the courtroom as detectives described her daughter’s slaying.

Blacksburg police investigator Desiree Twigger testified that she questioned Eisenhauer early on in the case and that Eisenhauer told her that he met Nicole online. The two had exchanged messages on Kik, a social media platform, and Eisenhauer said that he believed Nicole was 16 or 17.

Eisenhauer recounted how he and Nicole opened up to each other and shared an emotional connection. But when Nicole requested that they meet up, Eisenhauer demurred, the detective said, testifying that the college student said he “freaked out” when the seventh-grader referred to him as her boyfriend.

Twigger said that Eisenhauer admitted seeing Nicole the night she went missing but said that they only met briefly. When police asked him what he thought police should be doing, Eisenhauer replied that they should be “looking for a dead body rather than trying to interview the last person to see her alive,” Twigger said. He then stopped talking and requested an attorney.

Blacksburg police detective Ryan Hite said that Keepers crumbled under questioning, at first denying any involvement but later talking and turning over her phone. Keepers told Hite that she wanted to help them with their investigation.

Among the data found on Keepers’s phone was a text conversation she had with Eisenhauer shortly after Nicole’s slaying.

“I smell like cleaning supplies,” Keepers told him. “I mean I was close to a lot of blood.”

Keepers initially portrayed her role in the crime as minimal, saying that Eisenhauer had “forced” her to participate in disposing of Nicole’s body. But she later acknowledged that she helped with the entire plot.

Keepers told police about the preparation that went into Nicole’s death, including meeting with Eisenhauer for dinner at a fast-food restaurant where they planned for two options — Eisenhauer would knock Nicole unconscious and leave her to die of exposure to the cold, or he would approach the girl from behind, cover her mouth and slit her throat.

In the hours before Nicole’s killing, Keepers and Eisenhauer bought a shovel to bury the body, police said, and conducted a “dry run,” driving past Nicole’s apartment complex and then to Craig Creek Road, where Keepers selected the spot where the girl would be killed, noting its seclusion.

Eisenhauer left Nicole’s body in the woods for some period of time after he killed her, police said. Later, he returned with Keepers to retrieve the body, originally planning to bury it on property near Blacksburg belonging to his grandparents. But the two became concerned when Nicole’s disappearance drew considerable media attention, and the plan shifted. Police said the pair decided to drive Nicole’s body to North Carolina instead.

Police obtained a warrant in late April for the cellphone of a man who lived 40 miles east in Pulaski, Va., writing that Eisenhauer had texted the man about needing “a place to hide a body near you.” In another message, he said “original plan failed.”

Keepers told police that she helped Eisenhauer stuff the body into the trunk of the Lexus and that they then drove to the North Carolina border, where they dumped Nicole’s body on the side of the road, facedown and naked.

Hite testified that the pair disposed of Nicole’s clothing, backpack and the knife used in the killing in multiple places — throwing Nicole’s clothes into a trash bin behind a McDonald’s, her backpack off a bridge and into a river, and the knife into a forest.

Keepers told police that she helped plan Nicole’s death but was not present when Eisenhauer took the girl into the woods under the guise of a romantic walk.

Hite also said that Keepers texted Eisenhauer for an update on the plan that night.

Police said he texted back: “It’s done.”

Balingit reported from Washington.