Bath, England, 1892. Celebrated mystery author Lady Amy Lovell is set to tie the knot with Lord William Wethington, a fellow member of the Mystery Book Club of Bath. Amy's great-aunt, Lady Priscilla Granville, has offered to host their wedding at her stately Derby Manor House. But on the eve of the ceremony, the festive air in the drawing room is marred by Mrs. Alice Finch's argument with her husband, Albert, in another room. The next morning at the wedding breakfast, Alice falls face-first into her breakfast — dead.

When Amy and William's favorite detectives are summoned to the house, they see two champagne glasses in front of Mrs. Finch and none in front of her husband. Did Albert give his wife a poisoned drink? Always looking for the easiest solution, the detectives charge Albert with the murder. But Lady Amy is not convinced that Albert is guilty. There are too many things that don't add up.

In the hopes of being able to leave Bath and begin their honeymoon, Amy and William once again take things into their own hands. Suspects begin to pop up, but nothing takes them more by surprise than the discovery of a second body. Stuck in Bath until the whole poisonous predicament is solved, Amy and William are anxious to collar the perfidious poisoner and be on their way to their honeymoon. If they can't catch the killer, not only is their newlywed bliss under threat but they may not live to see happily-ever-after at all….