Someone knocked on the Cayedito's apartment door in the middle of the night.
Nine-year-old Anthonette Cayedito went to answer it. Who the visitor was is unclear, but authorities believe the visitor took Anthonette that night.
And more than 31 years later, Anthonette remains missing.
"It just broke my whole family up," Wendy Montoya, one of Anthonette's younger sisters, told the Albuquerque Journal last year. "It was a very dark and dysfunctional time."
It started the night of April 6, 1986. Penny Cayedito, Anthonette's mother, arrived home around midnight. Her three daughters had been at the family's apartment off Route 66 in Gallup, New Mexico with a babysitter. They were asleep when their mother got home. Penny went to sleep herself sometime before 3:00 a.m., according to local newspaper reports from the time.
Not long after, came that strange knock at the door. Penny, who was raising the girls on her own, didn't hear it. But Anthonette did. Her younger sisters remember her going to answer it, but she never came back to bed.
The next morning at about 7:00 a.m., Penny got up to take her children to Bible school and discovered Anthonette was not there. She immediately reported her missing.
An intense search was launched, but no one could find any traces of Anthonette.
One of Anthonette's younger sisters told authorities she thought the mysterious person at the door was one of their uncles, so police quickly questioned him. He was ruled out. Their first lead was a dead end.
About a year later, Gallup Police got a disturbing phone call. It was the voice of a young girl, who told them she was Anthonette and was in Albuquerque being held against her will. Before the call could be traced, police heard a gruff male voice saying, "Who said you could use the phone?" The line went dead.
It remains unclear if the call was simply a cruel prank or if the caller was really Anthonette.
Another strange lead emerged a few years later. A waitress in Carson City, Nevada told authorities she thought she saw Anthonette, who, by then, would have been a teenager. The girl she saw was sitting with an "unkempt" couple and looked to be in distress. After the group left, the waitress found a note under the girl's plate that read, "Help me! Call police."
Whether the story is true, and if the girl seen was Anthonette, also remains a mystery.
Anthonette's case remains open, the files kept in a box at the Gallup Police Department. A spokesperson for the department told Dateline there have not been very many tips in recent years. But every time a new detective joins the team, the case gets a fresh set of eyes to look at it.
Anthonette's mother Penny passed away in 1999, without any answers to what may have happened to her oldest daughter.
Anyone with information regarding Anthonette's case is urged to call the Gallup Police Department at (505) 863-9365.