Physik: Septimus Heap, Book Three

Dragons, shape-shifting cats, time travel and female Hanseatic traders all play a role in this third Septimus Heap book. There are also ghosts walking around and a rats that barely escape certain death by escaping on a dragon. There are also alchemist apprentices and other challenges.

And these are just the sideshows.

The main plot centers around Queen Etheldredda and her diabolical plot for immortality. That requires some harm to the main characters. But, of course they are not going to go down so easily.