Twelve-year-old Thea and her family are moving to a new town for a fresh start--her parents' bright idea. To Thea, it feels like running away. She lost her best friend, Charlie, in a tragic accident, and in the painful aftermath, she has gone mute. Her two younger sisters, however, are excited about moving, especially after their dad promises that the family will get a rescue puppy. This doesn't change Thea's mind, though, until Jack-Jack bounds into her life and makes it clear that he is no ordinary dog. As she bonds with Jack-Jack, and as the dog's mischievous ways steer her toward someone she can confide in, Thea opens up to the possibility of new friendships and forgiveness, and comes to believe in what cannot be fully explained.