Searching for a way to defeat the risen Apophis, Cleo discovers that he is destroying all the copies of the Book of Overcoming Apophis written by the magician Setne for some reason and the Kanes realize that there must be an important clue to defeating him in the book. They discover that there is one copy left in the Dallas Museum which is part of the Fifty-First Nome which is still loyal to the House of Life and travel there to get the book. They go on the night of the new moon when darkness is greatest which is the time that they know Apophis will attack from his previous attacks. The Kanes assemble a team made of themselves, Walt Stone, Khufu, Felix and Alyssa and travel to Dallas on Carter's griffin Freak.
Arriving at the museum, Carter pulls aside JD Grissom, leader of the Fifty-First Nome and informs him of the threat. He asks JD to allow them to take the scroll containing the book with them and convinces him by showing him a picture of the destroyed One-Hundreth Nome in Toronto. JD leads them into the museum, showing them the guards he has set up and Carter leads the group to the scroll. Sadie gets distracted on the way by a statue of her friend, the dwarf god Bes and is contacted by a mysterious face that appears in the wall to inform her that they won't save the scroll and even if they could, they'd never understand it without his help. He tells Sadie to save a golden box instead as it will give them a clue and that if they want his help, they have to get him out of some situation in two days by sunset but disappears before he can explain more. After JD disables the protection spells around the room with the scroll, they show him what they are looking for and explain why. Sadie examines it, but can't find any clues as to what is causing Apophis to be scared of the scroll and decides they need to take it so they can figure it out at Brooklyn House. At the moment, an explosion sounds from outside and they realize the Fifty-First Nome is under attack. Sadie lets JD go to help his wife and friends and he tells them to take the scroll. Before they can, Apophis' voice tells them that he will destroy them and the two obsidian criosphinxes guarding the door come to life.
Apophis starts the battle by having his criosphinxes destroy Felix's penguins to his horror. Khufu saves Carter from Apophis causing the ground to break apart where he was standing and start snaking across the room towards the Book of Overcoming Apophis, sucking up artifacts and destroying them. Sadie quickly uses the Divine Word drowah to erect a boundary between the line of destruction and the scroll, but the line of destruction starts to shred the shield while the power of Chaos tries to shred Sadie's mind. Sadie is saved by Walt who knocks her wand from her hand and breaks the spell, leaving Sadie with burned and steaming hands and nothing left of the Book of Overcoming Apophis but rubble and a hole in the wall where it had been. Sadie demands if Apophis is just going to destroy the scroll and leave without a fight, but he starts bringing statues to life to taunt them including a golden baboon which Khufu destroys. Apophis then brings to life a gilded wooden pharaoh to taunt them more before it disintegrates and another line of destruction heads for a golden cabinet. Remembering what the face in the wall said and possibly urged on by Isis, Sadie quickly orders the others to protect the cabinet as another explosion shakes the building. Alyssa attempts to stop the line of destruction with her power over earth, but Apophis quickly blasts through it and destroys her staff. Sadie tells the others that Apophis is trying to destroy the cabinet and they have to save it. Carter jumps in front of the path of destruction and erects a shield with his khopesh, but it nearly fails until Sadie challenges Apophis to destroy them now instead of waiting. Apophis stops the line of destruction and agrees, allowing Khufu to flee with the cabinet.
Apophis sends the criosphinxes after Sadie, but one slips in the water from the destroyed penguins and the other is attacked by a camel that was transformed from one of Walt's amulets. The camel, while not a great fighter, is able to pin the criosphinx with its weight, keeping it out of the fight. Apophis begins bringing exhibits to life to attack the magicians and the criosphinx who slipped battles Carter who tries to destroy it with his khopesh only to have it deflect his strikes. During all of this, a tornado of canopic jars pummeled Felix while he tried to fend them off with his staff, Alyssa is surrounded by an army of tiny shabti while trying to use her earth magic to keep the room in one piece and the statue of Anubis chases Khufu. Apophis' power was also causing the museum to shake and start to come apart around them. As Sadie tries to decide what to do, the second criosphinx throws off the camel and turns it back into an amulet with a blast of fire. Sadie decides that they have to restore Ma'at to survive and asks Walt to guard her while she does it. Sadie lowers her vision into the Duat in preparation and finds the room filled with the writhing coils of Apophis, representing his magic slowly expanding and encircling her friends. Sadie calls on Isis for help and the goddess shares her strength with Sadie who sees Carter as the war god Horus, Felix with a bright aura surrounded by what appears to be the hearts of evil spirits that attack him but were kept at bay by his powerful aura. Alyssa is shown to be surrounded by Geb who lifted his arms to the ceiling as she chanted and the shabti blaze like a wildfire. As Sadie looks at Khufu, the cabinet he is carrying opens and she sees something made of pure darkness which she doesn't understand and when she looks at Walt to ask him about it, she sees him shrouded in grey linen with transparent flesh and luminous bones representing his curse. The criosphinx he faces, which is the eye of the Chaos storm and has the face of Apophis in the Duat, lunges at Walt who binds it with an amulet that wraps golden chains around its face. Walt quickly tells Sadie to hurry and speak her spell as the criosphinx starts to break free of the amulet, Carter is backed up against the wall by the other one, Felix starts to fall with his aura failing, Alyssa starts losing her battle to keep the room intact and chunks of ceiling start to fall and Khufu is grabbed by the tail by the Anubis statue. Sadie channels the power of Isis and draws so deeply on her own magic reserves that she feels her soul start to burn and speaks the Divine Word Ma'at. Sadie focuses her energy on the spell and it restores order causing the coils of Apophis to burn away, the two criosphinxes to turn to dust, the caponic jars to fall and shatter, the Anubis statue to turn back into a statue and drop Khufu and the army of shabti around Alyssa to freeze. Alyssa is then able to repair the room and Apophis retreats deeper into the Duat. The effort of casting the spell causes Sadie to collapse.
After passing out, Sadie is visited by the spirit of her mother and Isis who are both impressed with what she did. Ruby tells Sadie for her not blame herself for "the deaths" and that when they make their plan, their father would object but they would have to convince him as it was the only way to save the spirits of the dead, including her. Isis tells her that they will soon merge again and rule the world before Ruby corrects her as saving the world from Apophis. Ruby and Isis disappear and Sadie ends up meeting with Anubis who tells her that while she's not dead, she came close. Anubis explains that he hasn't been able to see her in months as its against the rules, but with her as close to death as she is now, he can manage to communicate with her for a few moments. Anubis tells her they have the right idea and to look at what isn't there. As Sadie's heart starts to beat again, having briefly stopped after she cast the spell, Anubis agrees to meet with her in person briefly as they have something to discuss and she wakes up. Upon waking, she discovers that the King Tut exhibit is in ruins and that she was dead for two minutes before coming back. The group wonders about how the cabinet is supposed to help them as the Book of Overcoming Apophis was destroyed and then realize that the Fifty-First Nome was also under attack. Rushing outside, they find the Fifty-First Nome destroyed and all the magicians in it dead. The group repair as much as they can of the museum and leave
Upon returning to Brooklyn House, they try to figure out how the cabinet is a clue. Bast explains that its a shadow box, holding the shadow of King Tut. As they try to figure out what it has to do with defeating Apophis, Carter remembers that the shadow, the sheut is part of a person's soul. Talking about shadows makes Bast nervous and while she confirms that gods have shadows, she refuses to elaborate. Later that night, Horus visits Carter and while they are discussing things, Horus remembers that in Ancient Egypt, the word for statue and shadow was the same. Hearing this, Carter comes up with the idea of using Apophis' shadow in an execration spell against him and decides to ask Thoth since Horus doesn't know anything more on the subject. Discussing the situation, Carter, Sadie, Bast and Walt theorize that if they can capture Apophis' shadow in a shabti and destroy it, it will possibly destroy him and that Setne had written a spell to capture and destroy a shadow in his version of the Book of Overcoming Apophis and its why he's so eager to destroy those copies. Later, Anubis visits Sadie at a school dance and tells her that they have the right idea in using the shadow of Apophis against him, but that Thoth may not help them and they'd need other help. Anubis explains that the shadow acts as a back-up copy of the soul and the soul is not totally destroyed until it is. The shadow can be used to restore a destroyed soul and conversely if its destroyed, the being it is connected to will be destroyed as well, including gods. Anubis tells Sadie that Thoth could help if he could be convinced, but that they might need the help of the only magician crazy enough to research such a spell. Anubis tells her that the magician's trial is the next day at sunset, but before he can explain anymore about the nature of the sheut and the spell, he is dragged away by Shu and forbidden from seeing Sadie again. Carter and Walt later visit Thoth who is under attack by Apophis' demons because Apophis doesn't want Thoth helping them. Thoth confirms that the spell, which he calls a shadow execration could work against Apophis in theory, but while he can guide them a little, he can't help them get the spell or the shadow. Thoth confirms that like all sentient beings Apophis has a shadow and it can be used against him, but tells them that it is well hidden and he can't tell them where or how to use it as its against godly laws. Carter reminds him that the only other choice is to let Apophis destroy the world so Thoth offers a way to find out for themselves: Thoth had written a book called the Book of Thoth that contained a lot of information about the gods including where their shadows are located. The book was stolen in ancient times by the evil magician Setne who used it to create a number of spells, including the shadow execration. Thoth suggests that they could find Setne and get him to lead them to the Book of Thoth and use it to find and destroy the shadow. However, Setne is now a ghost and will be put on trial and destroyed at sunset so they only have so much time to get his help. At Setne's trial, they are able to secure his help and Carter, Zia and Sadie begin a quest for the shadow to use it to destroy Apophis.