Brown was last seen leaving her Burlington, Vermont apartment on March 15, 1976. She was accompanied by William J. Posey at the time. Posey was supposed to drive her to Connecticut to visit her boyfriend. He was incarcerated on drug charges and Posey told Brown he was about to be released early. Brown never arrived to see her boyfriend and has never been heard from again. When questioned about her disappearance, Posey said he had driven Brown partway to Connecticut, but he left her in Massachusetts after they found out Brown's boyfriend was not going to be released from prison after all.

Authorities believed Brown had been murdered, and Posey has always been the prime suspect in her disappearance and presumed death. Blood matching her type was found on the seat and floor of his car. He was convicted of kidnapping in her case in 1981 and sentenced to life in prison, but was not charged with murder, as Brown's body has never been located. Posey pleaded guilty to the abduction and murder of an Illinois woman in 1980 and is currently incarcerated in a North Carolina prison.

In 2008, Posey confessed to causing Brown's death after investigators promised him he would not face charges in connection with it. He is terminally ill. Posey says he never intended to take Brown to her boyfriend and only said he would as a way of luring her into his car. He then tried to convince her to help him sell cocaine, she refused, they got into an argument and he strangled her near the Shelburne Museum. He says he dropped her body over a guardrail on Interstate 89 in Vermont, but he can't remember exactly where. Brown's family accepted Posey's story and said they would hold a memorial service for her later in 2008.

Brown grew up in Enosberg Falls, Vermont. She graduated from Enosburg Falls High School and the University of Vermont. Investigators plan to renew the search for her remains.