Fourteen year-old Ark has the squittiest job on Arborium, the last forested island in the future.

A poor plumber's boy, he unblocks toilets in the city where he lives - a breath-taking, mile-high world carved out of the vast upper branches of a giant canopy of trees. Protected by a poisonous shield, he believes his forest kingdom to be the safest place on earth.

But while at work, he over hears a plot between a powerful councillor of the island and a secret spy from Maw, a superpower of glass and steel, that intends robbing Arborium of its wood, a natural resource now more precious than gold. Ark is plunged into danger and soon he finds himself on the run, fighting for his life.

Together with new found friends, he must travel from the highest tree-tops to the darkest roots of Ravenwood to save his home and his people.