At Tithe Hall, Lord Conrad Stockingham-Welt is busy instructing his servants to prepare for the apocalyptic disaster he believes will be triggered by the imminent passage of Halley's comet. The labyrinthine house is a nest of secrets and grudges, harboured by both staff and family members, who include an irascible and splendidly foul-mouthed maiden aunt, Decima. When Lord Conrad is discovered in his sealed study, killed by a crossbow bolt to the eye, she co-opts a new footman to help her find the culprit.