Circumstances of Disappearance
Sheila and her younger sister, Katherine, departed together from their family's residence on Plyers Mill Road in Kensington, Maryland on March 25, 1975 between 11:00-12:00. The girls were walking to the Wheaton Plaza Shopping Center in Wheaton, Maryland, which was approximately one-half mile from their home and located on the corner of University Boulevard and Veirs Mills Road. Sheila and Katherine were on spring vacation from school and wanted to see the Easter exhibits at the mall, as well as have lunch at The Orange Bowl Restaurant .

A neighborhood child saw the girls outside the restaurant at approximately 13:00. He told investigators that the sisters were speaking to an unidentified middle-aged man wearing a brown suit. The man was carrying a briefcase with a tape recorder inside. There were also other children around who were speaking into a microphone he was holding. The witness' description of the man led authorities to view the unknown person as a prime suspect in the Lyon sisters' case and a sketch of the individual was created.

The girls' older brother saw them inside The Orange Bowl Restauranteating pizza together at approximately 14:00. A friend stated that the girls were walking westward down Drumm Avenue, near Devon Street between 14:30 - 15:00. This would have been one of the most direct routes to their home on Plyers Mill Road from the mall and was the final confirmed sighting of the sisters. Their mother had instructed Sheila and Katherine to return to the residence by 16:00; when they did not arrive by 19:00, authorities were summoned and an extensive search was conducted. No evidence of the Lyon sisters' whereabouts could be located. The girls had less than $4 between them when they left home, and after eating lunch, would have had only some change left in their pockets.

A witness in Manassas, Virginia reported seeing two girls resembling Sheila and Katherine in the rear of a 1968 beige Ford station wagon on April 7, 1975. The witness stated that the girls were observed bound and gagged in the vehicle at approximately 7:30 that day. The driver of the station wagon resembled the man seen questioning children at The Orange Bowl Restaurant the day the sisters vanished. When the driver spotted the witness tailing him, he ran a red light and sped west on Route 234 toward Interstate 66 in Virginia. The station wagon had Maryland license plates with the possible combination "DMT-6**." The last two numbers are unknown due to the bending of the car's plate. The known combination was issued in Cumberland, Hagerstown and Baltimore, Maryland at the time. A search for matching plate numbers failed to produce any information.
The girls' disappearances remain unsolved.

Sketches of man wanted for questioning