Alex, the Dog and the Unopenable Door

Alex Jennings is a boy with a problem.
His mum's sent him away to boarding school because his father, the most famously failed explorer in the history of the Cusp, has escaped from hospital again, yelling 'squiggles'.
Make that two problems.
Now the evil Davidus Kyte and all his henchmen are after Alex, convinced he alone knows the meaning of the word 'squiggles'.
OK, make that three -
Alex Jennings is a boy with a lot of problems. But with the help of a talking dog and a girl with unfeasibly sharp teeth, he just might have what it takes to cross the Forbidden Lands, escape the evil Davidus Kyte, and find out what lies beyond the Cusp . . .