Two years ago, the body of 13-year-old Kathleen Murphy of West Hyattsville was found in a creek near her home. Although two dozen police officers combed the county for suspects in the days afterward, they had no success, and the investigation finally was abandoned.

Early the week, Kathleen Murphy's parents received a letter from a man in rural Virginia who claimed he had information about the case. The next day, they received a phone call from the same man.

Yesterday morning, the caller, Randolph Alan Gaul, 31, of Glencoe, Ill., who once lived a few blocks from where the girl's body was recovered, was arrested and charged with Kathleen Murphy's murder.

Gaul has been charged with first-degree murder and is being held without bond at the county detention center in Upper Marlboro. He is expected to appear for a bond hearing there today.

Murphy's parents would not discuss the letter or call they received from Gaul. But the victim's mother, Mary Murphy, said yesterday: "We've been living a nightmare for the past two years."

According to county police, the Murphys received a letter from Gaul on Monday and notified police. On Tuesday, he called them and indicated he was staying in a motel in Bedford, Va., in the foothills of the Blue Ridge Mountains.

At 6:30 Wednesday night, Virginia State Police, after being notified by county police officials, picked up Gaul, and county detectives brought him back to Upper Marlboro for questioning.

A police spokesman said Gaul had waived extradition.

Kathleen Ann Murphy disappeared on the night of Aug. 23, 1978. When her mother asked her to sleep at home instead of staying at a friend's house late that night, she took a shortcut home through a nearby park and never made it home.

The next morning her nude body was found lying face down in the shallow water of the Sligo Creek, with a large rock on top of her head. Police combed the area for suspects, but no arrests were ever made.

Two neighborhood youths later told police that they had seen Murphy, a student at Rollingcrest Junior High School, near a bridge over Sligo Creek at the corner of 17th Street and East-West Highway shortly after midnight. The bridge where she had been seen was a short-cut between her home -- located on Dayton Road -- and the friend's house.

When Murphy did not return home that night, her mother assumed her daughter had decided to stay at the friend's house. The friend, meanwhile, assumed she had gone home.

No one knew Murphy was even missing until the following morning when her body was found by some workmen.

Murphy was the youngest of nine children. Her father, Thomas, is an executive with a Washington hotel.

According to police, Gaul lived in the same neighborhood in West Hyattsville as the Murphys and was employed at an apartment development. A police spokesman said he had left the area some time ago and had been traveling in the last few months.

The Murphy's neighbor expressed relief yesterday at word of the arrest.

"The whole block was shocked [at the slaying]," recalled Mabel Emmert, who has one daughter. "You'd go to bed at night thinking 'Who did it?' and 'Are they still in the neighborhood?'"

A man who said the slaying occurred near his house recalled that "it really shook everyone up. Two years ago the cops came around, told us 'We'll take care of it,' but said so far they had nothing.

"You'd say to yourself, 'Well, if the cops can't do anything about it, that's about it -- it's one of those unsolved crimes and there's nothing you can do about it.'"