Bridgerton meets Agatha Christie in this dazzling fourth installment to the captivating Regency-era Lady Petra Inquires mystery series.

London, December, 1815. It's Christmastime, and Lady Petra Forsyth is assisting the Lady Patronesses of Almack's Assembly Rooms with four bachelor-auction dances to be held in the fortnight before Christmas Eve. With one eligible young lady per night winning the right to dance with the four eligible bachelors-called "the Merry Gentlemen" in a nod to the season-it's sure to be a delightful event.

Until the first dance, when Petra and a group of science-minded young ladies discover the dead body of one of the bachelors. The death is deemed an accident, but when another bachelor's life is nearly ended, Petra fears something sinister may be afoot. What's more, Petra's young friend Teddy has arrived at her door, begging for help. His long-absent mother has been imprisoned, and Teddy is certain she is innocent of her crime.

Time is of the essence in both cases, and Petra is asked to investigate from within by pretending to be one of the ladies vying for the bachelors' attentions. Indeed, it's enough to make an obstinate headstrong girl scream.

As she works to unravel the truth, Petra will need to act like a lady-a Lady Patroness, that is-think like an enterprising scientist, and use every investigative tactic she's learned to solve two mysteries before she becomes the next target.