The titular Ink Thief steals the power of children's imaginations by removing ink from books and drawings, dragging young siblings Sam and Jim into his fantastical world of Bumps and Oobs.
After moving to a new home, siblings Sam and Jim stumble onto the lair of the nefarious Ink Thief, where they meet mysterious librarian Miz Tiggle and other strange creatures who go bump in the night.
When Jim is lured by The Ink Thief's charm, Sam turns to the Bumps in an attempt to save her brother.
Sam learns The Ink Thief's origins, Miz Tiggle calls a meeting of the Official Organisation of Bumps, and Jim discovers a page which provides his captor with immense superpowers.
Sam and Mizz Tiggle travel through the Apopalyptic Spiral to reunite the Four Bumps of the Apopalypse. Meanwhile, Jim discovers The Ink Thief can increase his power by stealing the lifeforce from other Bumps.
Dog tries to protect the library as Sam, Miz Tiggle and Snoop go to meet Rock. Meanwhile, The Ink Thief drains his powers faster than his minions can collect more.
Miz Tiggle finds the other two Bumps of the Apopalypse. Also, Snoop stands up to The Ink Thief and his cronies in an effort to protect Dog.
Things go south for The Ink Thief when the Four Bumps of the Apoplypse infiltrate his domain.
