In Regency England, an exotically dressed woman is found in the fields, speaking a language no one can understand. She ends up at the home of the Worrall family, the local gentry. Frixos, the Greek butler, suspects she is a fraud from the start, quietly laying the groundwork for a careful judgment about her origins. Mr Worrall soon dispatches her to the magistrate to answer for vagrancy, but Mrs Worrall steps in to offer care instead, changing the course of her fate.
Meanwhile, Gutch, a local printer and newspaper reporter, becomes intrigued by the case, especially after the woman communicates through mime that she might be Princess Caraboo. Gutch digs into the story, interviewing farm workers who found her and uncovering that she carried a book from the Magdalene Hospital in London. As the Worralls depart on a trip, the servants peering into her situation discover a tattoo, a mark they associate with natives of distant lands, and are stunned to learn that Princess Caraboo bears such a symbol on her thigh.
Frixos later confides to Gutch that he now believes Princess Caraboo might be genuine, a claim that unsettles the cautious gates of the household and adds another layer to the mystery. Mrs Worrall’s strategic use of Caraboo’s presence becomes a way to attract investors for a spice trade venture, hinging on her imagined return to her homeland. Into this mix steps Professor Wilkinson, a linguist who is initially skeptical and quick to dismiss the possibility of a fraudulent act, yet his doubt keeps him from declaring her a hoax outright.
Society in the region becomes captivated by Caraboo, and grand gatherings, parties, and soirees turn her into a centerpiece of curiosity and wonder. Gutch begins a deeper probe into the people connected with the Magdalene House, while Lady Apthorpe escorts Caraboo to a ball hosted for the Prince Regent, a contemporary icon who is fascinated by her presence.
The truth begins to tighten around Caraboo when Mary Baker—the woman behind the disguise and the one who formerly worked as a servant for Mrs Peake—is identified by those who knew her. She is promptly locked up as the pieces of the puzzle threaten to reveal the whole deception. Pressure mounts as the local magistrate and Mr Worrall push toward punitive measures, even as Mrs Worrall provides M. Gutch with documents that implicate her husband and the magistrate in a bank fraud scheme. These revelations become leverage for a grim bargain: if Mary Baker can go to America, the story can be buried.
Yet Gutch, harboring growing affection for Mary, resists the urge to hush the truth. Instead, he uses the incriminating evidence to strike a deal that would spare her from punishment, offering to take her away to the United States. In the end, love and risk collide as the reporter and the enigmatic woman depart together, choosing a future beyond the courtroom and the gossip-filled halls of society.
