The story focuses primarily on the 500-year-old spirit of Queen Etheldredda, who attempts to use Septimus Heap to attain immortality.

She sends Septimus to meet her son Marcellus Pye who drank an incomplete potion of immortality.

Snorri, Jenna, and Nicko fall through the glass, but it's shattered when Spit Fyre attempts to follow them through it.

She escapes when she meets Septimus by chance at a feast thrown to honor the return of the princess.

Reception for Physik was positive[1][2] receiving favorable reviews from ALA Booklist, Publishers Weekly and School Library Journal.