The night was extremely cold (well below zero), so cold that a search plane later crashed due to the freezing temperatures. Before disappearing, Dr. Kilcoyne was excited about a major breakthrough in her hypertension research, even believing it could win her a Nobel Prize. While her colleagues confirmed a breakthrough, they didn’t think it was as significant as she did. She showed unusual behavior before disappearing: buying lots of groceries (in multiples of three!) and liquor, claiming she was having a party and press conference to announce her research, but she made no such arrangements.

Days later, some of her belongings—passport, checkbook, and wallet—were found neatly arranged near her house, in a spot already searched. A blouse was found rolled up and inside-out some distance away, suggesting it was deliberately placed there.

Her brother had been worried about her mental state due to stress from work; he’d spoken to her the day before she vanished, and she was very agitated, claiming to be spied upon. He’d even scheduled a psychiatrist appointment for her.

The leading theory is that she died by accidentally or intentionally entering the freezing ocean, possibly while experiencing a mental health crisis. Her family believes this, but some investigators are unsure, and her disappearance remains a mystery. She was declared legally dead in 1989. Police don’t suspect foul play.