WHY IT’S SO MYSTERIOUS: Over the years, countless theories emerged. Some believed Dorothy died by suicide over her failed writing career or an unrequited love (could the book she bought about engagements be a clue?). Others suggested she died during a botched abortion, and her body had been quietly disposed of. A few speculated she was murdered in Central Park or kidnapped right off the street.

One popular theory? She faked her own death and fled (perhaps to Europe) to start over. She had, after all, bristled against her parents’ protectiveness (her father, for example, had refused to let her get an apartment of her own). But despite alleged sightings of her everywhere from Philadelphia to Texas (later discredited), and at least two women who claimed to be Dorothy (all proven to be impostors), there simply was no proof of this.

Her heartbroken mother died in 1928, still hoping for answers, while her father, who dismissed the idea that his daughter would ever “disgrace” the family by sneaking off without a trace, passed away a few years later. In one of his final interviews, he declared, “After all these years, I am convinced that Dorothy is dead.”