Augusta Lockwood is still wrestling with the dilemma of an anonymous corpse buried beneath her floorboards, when a new mystery arrives on her doorstep. A governess friend from the secret ladies society presses Augusta into helping to identify the culprit behind a series of deadly goings on in a great house under shadow.

Insinuating herself into the home, Augusta must navigate a tangled web of deceit and suspicion, leading everywhere from the downstairs servants to the strangely cold family that employs them. But can Augusta cope with two investigations at once, when a mysterious intruder from the past returns to finish a dastardly task?