Twelve-year-old Jessie is in for a long, lonely summer at her aunt and uncle's house. Her uncle is clueless, her aunt is downright frosty, and worst of all, her cousin Ann thinks Jessie isn't cool enough to hang out with anymore. But Jessie is industrious, and--not content with being ignored all summer--she convinces Wes, a grouchy neighborhood dog walker, to take her on as his apprentice. Sure, dog walking turns out to be harder than she expected, but she has Wes's dog-walking code, the Rules of the Ruff, to guide her, and soon, she's wrangling her very own pack like the best of them. But when Monique, a charming rival dog walker, moves to town, she quickly snatches up most of Wes's business--and Jessie decides she isn't going to take this defeat with her tail between her legs.