"Harry Dresden's faced some pretty terrifying foes during his career. Giant scorpions. Oversexed vampires. Psychotic werewolves. It comes with the territory when you're the only professional wizard in the Chicago area phone book.
But in all Harry's years of supernatural sleuthing, he's never faced anything like this: the spirit world's gone postal. All over Chicago, ghosts are causing trouble — and not just of the door-slamming, boo-shouting variety. These ghosts are tormented, violent, and deadly. Someone — or something — is purposely stirring them up to wreak unearthly havoc.
But why? And why do so many of the victims have ties to Harry? If Harry doesn't figure it out soon, he could wind up a ghost himself...."
Set a year after the events of Fool Moon, Dresden and his friend Michael Carpenter do some ghost hunting and then are nearly captured by his overprotective faerie godmother Leanansidhe, escaping only to be arrested by the Chicago police.
Harry is bailed out by his girlfriend Susan, and receives an official invitation to represent the White Council at a Red Court vampire party. He's politically required to go, but forbids Susan to follow, despite her reporter's curiosity.
Helping Murphy and Father Forthill with the hunted Lydia, Harry is attacked by vampires and sent into a narcotic slumber, dreaming of being attacked by a demon called the Nightmare, who appears to be allied with Kravos, the sorcerer he, Murphy, and Michael arrested after the events of the previous book. Awakening, he finds out that the Nightmare's dream attack was potent—he's been drained of much of his magic. Harry deduces that Michael and Murphy will be attacked next but arrives too late, managing to scare the Nightmare away only after he's already hurt Murphy and arriving again too late to stop the demon from kidnapping Michael's wife Charity. The demon was disguised as Harry himself both times.
Dresden tracks the Nightmare to a cemetery and attacks it, when Leanansidhe appears as Dresden is beaten down. In exchange for a pledge of service, his godmother points out the water streams around the cemetery, and Dresden tackles the Nightmare into one, causing it to melt into ectoplasm. Dresden picks up Amoracchius, intending to use it against his faerie godmother, but the sword wrenches out of his hands and lands at the faerie's feet. Since Dresden defiled the holy blade by attempting to use it in an act of treachery, Leanansidhe is able to pick it up and steal it.
Dresden calls on assistance from a friend in Chicago PD to get Kravos's journal from the evidence lockers in order to learn the name of the demon. Since Dresden cannot determine which of his enemies is controlling the Nightmare, he casts a spell that binds the Nightmare to focus its attention only on him.
When Dresden bound the Nightmare to him, he felt the presence of the sorcerer that was controlling it. He and Michael go to Bianca's party reasoning that it's unlikely to be a coincidence, and that they may be able to identify the person there. At the entrance, they meet Thomas Raith, the representative of the White Court vampires, and his human date Justine. Thomas facilitates Dresden's introduction to the vampires, who poison him with narcotic vampire venom. Michael keeps Dresden on his feet so they can find the sorcerer. Susan arrives with a forged invitation; due to this breach of hospitality, the vampires are free to kill her.
To make matters worse, Leanansidhe is present and her proximity further weakens Dresden due to his broken promise to her. Susan bargains with her to cure Dresden in return for a year of Susan's memory, but not specifying what form that would take. The faerie seals the bargain and leaves Susan with no memory at all of Dresden - the year taken was not contiguous, but rather consisted of every moment Susan had spent in Harry's presence.
As Harry and Michael attempt to get Susan out of the party, they encounter Michael's old foe, Mavra of the Black Court vampires. Dresden senses that she is the sorcerer manipulating the Nightmare. Leanansidhe reappears to gift Amoracchius to Madame Bianca. As part of the evening's entertainment, Mavra intends to unmake the sword with the blood of an innocent person, Lydia. It's an obvious trap; Dresden and Michael will have to violate the rules of hospitality and the Unseelie Accords—potentially triggering war between wizards and vampires—in order to save Lydia and the sword.
As the Red Court vampires surround them, Thomas explains that he and Justine are also marked for death and offers to help Harry in return for protection. Bianca captures Justine and holds her ransom with the price of Thomas betraying Dresden. Thomas agrees and pushes Susan into the mob of vampires. Bianca double-crosses him and keeps Justine, ordering Thomas' death. He flees while Susan is dragged away screaming. Burning with rage, Dresden incinerates everything in the immediate vicinity and collapses, exhausted. Michael carries Lydia and Dresden out of the inferno.
Dresden regains consciousness a day later. He's slightly burned but Lydia is safe and asleep. Michael has been guarding them in spite of his own wounds and the poor health of his wife and newborn child. Thomas arrives to propose that they work together to rescue Susan and Justine. As an offer of good faith, Thomas returns Amoracchius.
Lydia awakens, possessed by the Nightmare, and attacks them. Thomas subdues her using his vampiric powers and Dresden exorcises the spirit. His attempts to control it using the demon's name fail and he realizes the culprit is not the demon at all; it's actually the ghost of Leonid Kravos himself, using the demon's shape to distract Harry. Mavra used the torment spell to stir up the spirits, which in turn weakened the barrier between the real world and the Nevernever, thus allowing Kravos to become a more powerful ghost when he committed ritual suicide in his jail cell. Mavra had also been teaching Bianca sorcery, making her a more powerful adversary.
The group decide to journey through the Nevernever to sneak into Bianca's house, but en route, Leanansidhe attacks and captures Dresden. He strikes yet another bargain with her, extracting a promise that she will not bother him for a year and a day. Bound by it, she releases him. However, as Michael and Thomas made no such bargain, she attacks them instead. They urge Dresden to go ahead without them and rescue Susan and Justine while they hold off the faerie and her Hellhounds.
Dresden returns to the real world inside Bianca's house, which turns out to be a trap. Dresden is captured by Bianca and locked in a room with Justine and Susan. Susan has been partially turned into a vampire, a process that will be completed if she kills a human through vampiric feeding. Dresden manages to restore her memory with magic, and he reinforces Susan's self-control and defuses her thirst by finally admitting his love for her.
Together, they seduce Kravos to kill Harry. But due to the weakened barrier, Harry's ghost forms even after Susan revives him and together the two Harrys defeat Kravos. Dresden consumes the Nightmare's essence, taking back the lost portion of his power and Kravos' power as well, getting supercharged with black magic. They try to escape, but are stopped by Bianca, who offers a compromise: Dresden gets Justine, his magical items, and safe passage; in exchange, Bianca gets Susan. If Dresden refuses and tries to rescue Susan, there will be war between the vampires of the Red Court and the White Council. Dresden fights back with a powerful spell that exploits the thinned barrier with the Nevernever to rouse the spirits of all the vampires' victims against them. The wrath of the empowered spirits destroys the mansion and the vampires, while Dresden, Susan, and the others escape.
After the battle, Susan disappears; her apartment is up for rent and she's not at her job. Dresden tracks her down to a secluded cottage and proposes marriage, but Susan refuses, leaving him a love note as she flees the country. The final note of the book is the White Council will be visiting Chicago as a war has broken out between the Red Court and the Council.