When their over-the-top ideas expand their amazing treehouse to include a giant submarine sandwich shop and a human pinball machine, Andy and Terry find themselves babysitting Mr. Big Nose's three troublesome grandkids.

For all the books they have written, Andy is the narrator and Terry is the illustrator, but when Terry tries to narrate too, the story goes out of control and they must evade the Story Police, who want to arrest them for crimes against storytelling.