Plot summary

Here is a short summary of the plot. Don't read it if you are planning to read the book in future...

Josh and Sophie Newman have fled to Paris with Nicholas Flamel and Scratach. The Dark Elders want to get them because they have two pages from the Book of Abraham. With these pages the Dark Elders could dominate the world.
They seek an old friend of Nicholas, called the Comte de Saint-Germain (or Germain) and his wife Joan of Arc. Germain teaches Sophie Fire magic, while his wife learns her how to control her magic. Nicholas gives Clarent, alegendary magical sword, to Josh.
John Dee, a servant of the Dark Elders, sends three Disir (also known as Valkyrie) after them. The Disir bring an ancient monster called Nidhogg to kill Scratach, but instead the monster captures her. Josh tries to free her with the sword Clarent, but the monster escapes to the Seine. Josh follows, and one of the Disir follows him. The other two Disir fight Sophie and Joan of Arc, but they finally lose. Flamel arrives as well, and together with Joan and Sophie he follows Josh.
In the meanwhile Josh is fighting Nidhogg at the bank of the Seine. He almost gets killed, but then he is saved by Dee. Dee convinces Josh to come with him. He tells Josh he can bring him to someone who will awaken his powers, and Josh believes him. They go into the Catacombs of Paris beneath the Notre Dame.
When Sophie arrives at te Seine she kills Nidhogg, but Scratach gets pulled into the water by the evil creature Dagon.
Nicholas and the others follow Dee them from the Seine, but when they find him his powers are being Awakened by Mars Ultor, the God of War. Nicholas manages to let Josh escape, and they flight.
Outside, Dee tries to kill them by sending an army of awakened statues, but Josh and Sophie combine their powers, which makes them extremely powerful. They destroy the statues and escape from Dee. The next day they flight to London.