In 1937, LIFE Magazine launched the career of an up-and-coming starlet in a multiple-page photo spread that, overnight, made “Cynthia” a household name. In very short order she became an A-list celebrity; was given her own television talk show and starred on the silver screen; was sent jewels and dresses by top fashion houses; was briefly engaged to one of radio’s biggest stars; hobnobbed with the former king of England; and became one of the most recognizable faces in the fashion world.

There was only one minor catch: Cynthia was a mannequin. Not a mannequin in the way a supermodel is a mannequin. But a mannequin mannequin. A made-of-plaster mannequin.

Cynthia’s story begins in a small Midwestern town in the early part of the 20th century. Her creator, Lester Gaba, was a Hannibal, Missouri, shopkeeper’s son with dreams of a grand life in the big city. He achieved it through his uncanny skill at one of the Great Depression’s quirkier national crazes — soap sculpting. Buoyed by the fame he earned as a soap sculptor, Gaba moved first to Chicago, then to New York City in 1932, where he went into fashion and retail and pioneered the design of department-store windows. (It’s rumored he moved to New York to be close to his reputed lover, Vincent Minelli.)

Once she achieved a certain level of fame, gossip columnists began writing about Cynthia as if she were a real socialite making the rounds at parties around New York. When partygoers tried to engage the mannequin in conversation, Gaba begged off by claiming she was suffering from a touch of laryngitis.

Hers was a stranger-than-fiction tale that encompassed the highest circles of New York and London society, the very the lowest brow of American entertainment — and even (as so many improbable, compelling stories so often do) touched on a grisly murder investigation.