Employed by the Revere Copper and Brass Company, Welden's father was the designer of many familiar household utensils, as well as stylish cocktail shakers and other objects.

One day, Welden resolved to find and walk a portion of the Long Trail, a hiking route located a few miles from the campus.

[4][page needed] On December 1, after finishing her shift in the Bennington College dining hall, Welden returned to her room and changed into walking clothes.

Local contractor Louis Knapp picked Welden up and drove her as far as his house on Route 9, about 2.5 miles (4.0 km) from the Long Trail.

Over the next couple of days, Welden's visit to the Long Trail was discovered when one of the hikers she had approached identified her from the photo in the Bennington Banner newspaper, where he worked.

[7][8][9] Alternative theories speculated that Welden had been in unusually high spirits and had decided to run away to start a new life, was going to meet a secret lover and eloped with him, or had become injured and suffered from amnesia.

He stormed off in a jealous rage shortly thereafter and, depending on different statements he made, went to his shack and spent the evening by himself or he drove up the travel portion of the trail (where Welden was heading).

[12] When no evidence was found that a crime had been committed, no body was discovered, and no forensic clues were identified, this avenue of the investigation ended.

[4][page needed][13][14] The manner in which Welden's disappearance was handled by local law enforcement was sharply criticized by her father and many others.

[18][19] Other female hitchhikers disappeared under similar circumstances within the New England region during the same time period and there has been speculation that all three might have been victims of the same unidentified serial killer.

Constance Christine "Connie" Smith, a 10-year-old girl, ran away from Camp Sloane in Lakeville, Connecticut on July 16, 1952, and was last seen hitchhiking along Route 44.

Since Connie Smith appeared to be older than she actually was, one author speculated that she might have been a victim of a serial killer with a preference for young women in their late teens, such as Welden, or early twenties, such as Hull.