In six weeks, she’d be the most famous missing woman in New York City.

Wearing a tailored blue coat and stylish black velvet hat, Dorothy, a Bryn Mawr grad, left her parents’ home at 108 East 79th Street to shop for a gown at a Fifth Avenue department store.

After running into a friend and chatting about an upcoming society function, no one saw her again.

It was unlike Dorothy to just take off; she was known as a stable young woman making a go at a career as a writer.

“The Arnold family, eager to avoid scandal, kept the disappearance a secret from both the press and the police for six weeks, drafting private detectives instead,” wrote Andrew Roth in Infamous Manhattan.

By late January, when no trace of Dorothy turned up, they went public. Immediately, journalists dug up dirt.

Dorothy was having an affair with a Philadelphia man, but he claimed to know nothing of her whereabouts.

After thousands of dollars were spent looking for her and years passed, the case went cold.

“Various rumors claim that she died during an abortion, that she fell overboard from a ferryboat, or that her parents had banished their pregnant daughter to Switzerland,” wrote Roth. “Her disappearance remains a complete mystery.”