Fenway and his beloved short human, Hattie, are the perfect pair. She loves romping in the Dog Park, playing fetch, and eating delicious snacks as much as he does. But when they move from the city to the suburbs, there's bad news. While Fenway's hard at work deterring intruders and battling a slippery floor, Hattie starts changing. She hangs out in a squirrely tree house. She plays ball without him. What could be happening? Crushed and confused, Fenway sets out on a mission. He's going to get his Hattie back and nothing will stop him.