Margaret Mary Kilcoyne

Margaret Mary 'Peg' Kilcoyne was a 50-year-old cardiologist and assistant professor of medicine at the Columbia College of Physicians and Surgeons in New York, where she researched treatments for hypertension. According to the Nantucket Current, she was the first woman to graduate with an M.D. from the University of Vermont's medical school, in 1964, and had owned a vacation home in the Tom Nevers area of Nantucket, Massachusetts, since 1970. In January 1980 she told family, friends and colleagues that she had made a major breakthrough concerning the hormone angiotensin in the brain — a discovery she believed could win her a Nobel Prize. Colleagues later said her work was genuinely promising but less momentous than she believed, and her brother Leo grew concerned after a lengthy, rambling phone call in which she spoke rapidly and seemed elated.

In the days before she vanished, witnesses described unusual behavior. She bought roughly $645 in groceries and about $200 in liquor at a local market, telling staff she was planning an announcement party or press conference, though no arrangements were ever made. Traveling to the island, she approached a stranger in Connecticut, described herself as a 'nervous wreck,' and offered the woman a job in her laboratory. On the evening of January 25, 1980, she dined at her Nantucket home with Leo and two island friends, Richard and Grace Coffin, who described her as 'hyper.' She went to bed around 10:00 p.m. When Leo went to wake her for church the next morning she was gone; her winter boots, only coat, watch and purse were still in the house. He reported her missing at 7:15 a.m.

A two-day search involving about 45 personnel — Nantucket police, State Police, firefighters, divers and a Coast Guard helicopter — covered the island's east end, moors, cranberry bogs, ponds and shoreline without result. Then, on February 3, 1980, dog walkers found Kilcoyne's passport, savings book, sandals and a wallet containing a single $100 bill stacked neatly at the edge of a clearing near Philips Run swamp, about a mile from her home, in an area that had already been searched. A brown blouse was found placed under nearby brush. Investigators' initial theory, supported by her brother, was that she had taken her own life, possibly by walking into the ocean during a manic or psychotic episode.

The case never fully settled into that explanation. In March 1980 a deputy sheriff's chemical tests reacted positively for possible blood in her bedroom and bathroom, though he concluded the results could have innocent explanations. According to the Nantucket Current and N Magazine, several investigators later voiced doubts: a State Police trooper noted an unlogged light aircraft had left the island early that morning, and some former officers speculated she had staged her disappearance or been helped off the island, while others suspected foul play. A colleague, neurologist Earl Zimmerman, concluded she likely suffered from an undiagnosed neurological illness and called the case 'a medical tragedy.' The original police case files reportedly later went missing from department records.

Kilcoyne's brother obtained receivership of her property in 1980 and she was declared legally dead in July 1989; Leo Kilcoyne died in a 1992 car accident. Her body has never been found, no confirmed sightings were ever verified, and her disappearance — listed with NamUs and the Doe Network — remains one of Nantucket's most enduring unsolved mysteries.