Queste by Angie Sage

There's trouble at the Castle, and it's all because Merrin Meredith has returned with Darke plans for Septimus. More trouble awaits Septimus and Jenna in the form of Tertius Fume, the ghost of the very first Chief Hermetic Scribe, who is determined to send Septimus on a deadly Queste. But Septimus and Jenna have other plans—they are headed for the mysterious House of Foryx, a place where all Time meets and the place where they fervently hope they will be able to find Nicko and Snorri, who were trapped back in time in Physik. But how will Septimus escape the Queste?

Queste, like all the books in the Septimus Heap series, is filled with nonstop action, humor, and fantastical adventure as Septimus continues his journey of Magykal self-discovery.