The killing of an 11-year-old girl found in Sandown remains unsolved after 55 years.Last seen: Jan. 29, 1969Body found: Aug. 10, 1969Case status: Unsolved homicideDebra Horn disappeared from her Allenstown home on Jan. 29, 1969, authorities said.She slipped on ice and bumped the back of her head walking to school that morning, according to a report at the time from the Associated Press. Horn asked to stay home that day, and she was home alone that morning while her parents were at work, the report said.When the parents returned home for lunch, she was missing. Her father was convinced she had been abducted, the Associated Press said in the report.Officials at the time said Horn was last seen wearing a light gold jumper, white turtleneck and gold knee-length socks. Authorities said teenagers found her body in the trunk of an abandoned car in Sandown over six months after she went missing. Her body had badly decomposed, officials said. A cause of death could not be determined because of how much the body decomposed, according to a separate AP report. Horn's English tutor, Luella Blakeslee, went missing a month before Horn's body was found. Blakeslee's remains were found in a shallow grave in 1998. It is not known if these cases are connected.Can you help police solve this case? Submit a tip to the New Hampshire Cold Case Unit.