Gideon is an indentured servant in the Ninth House, her freedom curtailed by her childhood nemesis: the necromancer Harrowhawk. When the Emperor invites Harrowhawk to partake in a deadly trial, she cajoles Gideon into joining. What follows is a kind of haunted house mystery, in which Harrowhawk attempts to uncover the secrets that will make her immortal, while Gideon tries to keep both them and her newfound crush alive. The tale is hilarious and romantic and gory in equal measure, and I loved every minute of it.