Calista Langley operates an exclusive “introduction” agency in Victorian London, catering to respectable ladies and gentlemen who find themselves alone in the world. But now, a dangerously obsessed individual has begun sending her trinkets and gifts suitable only for those in deepest mourning. Desperate for help and fearing that the police will be of no assistance, Calista turns to Trent Hastings, a reclusive author of popular crime novels. As Trent and Calista comb through files of rejected clients in hopes of identifying her tormentor, it becomes clear that the danger may be coming from Calista’s own secret past.