THE MITFORD MURDERS

Fellowes transitions from providing the history behind the fiction (Downton Abbey—A Celebration: The Official Companion to all Six Seasons, 2015) to adding some fiction to history in her first mystery based on the life of the legendary literary Mitford sisters.

Florence Nightingale Shore, a dedicated war nurse in the model of her godmother and namesake, was attacked on a Brighton line train on Jan. 19, 1920, and died a few days later. This much is historical fact, and it’s equally true that her killer was never found. But what if her murder had drawn the attention of Guy Sullivan, a dogged young member of the railway police determined to make a name for himself, and 16-year-old Nancy Mitford, the eldest of Lord and Lady Redesdale’s seven children, gifted with an adolescent’s grisly imagination and eagerness to break out of the nursery? The two are linked by Louisa Cannon, the daughter of a recently widowed washerwoman. Louisa is desperate to escape the poverty of London, where her predatory uncle is trying to steal her last shreds of respectability. A chance encounter with an old friend who married well leads Louisa to a recommendation for a job as the new nursery maid for the Mitford brood—a job she can reach only by fleeing her uncle’s grasp on a desperate train journey. Along the way, Guy Sullivan saves her and is instantly smitten. Nancy’s keen interest in the case, Louisa’s immense gratitude to the family, and Guy’s determination to do real police work (and see Louisa again) all culminate in a grand confrontation with the killer at Nancy’s 18th-birthday ball.

The solution to the puzzle feels a bit implausible, but the heroine is appealingly plucky, and the reader sinks into the rich period detail as pleasantly as into an overstuffed sofa.