Nine-year-old Mary Lou and her 11-year-old cousin, Billy were last seen in Albuquerque, New Mexico on September 22, 1979 in the vicinity of Edith Road and the 300 block of Mountain Road northeast in the Martineztown neighborhood. They left to go to the post office and never returned. Neither of them have been heard from again.
The circumstances of the Sena children's disappearances are unclear.
There are theories that they ran away, were abducted or accidentally got locked into a railcar while playing. There were rumors that they had been murdered and buried in the basement of a house in the Martineztown area, but this story was never confirmed.
Authorities identified a possible suspect in Billy and Mary Lou's disappearances in 2011: Michael Cordova, who was the live-in boyfriend of Billy's mother in 1979. Billy's sister stated that Cordova was a drug dealer and grew marijuana in the family's backyard.
His sister remembers that shortly before Billy and Mary Lou vanished, one of Cordova's marijuana plants went missing. Cordova blamed Billy for it and severely beat him. Authorities are trying to find and question Cordova, and they're also looking for a woman named Liza Ramirez, who lived at Billy's residence in 1979.
Most of the Sena children's relatives are deceased, but Billy's sister and Mary Lou's mother are alive. Their cases remain unsolved.
Mary Lou is of Hispanic descent & has black hair and brown eyes.
Billy is of Hispanic descent with brown hair, brown eyes, a birthmark on his left shoulder blade and a strawberry birthmark under his ribs on the right side of his back.