One in six dogs goes missing at some point, leaving bereft owners to search high and low, hang "missing" posters, check shelters, and hope for good news. While Susannah Charleson studies animal behavior, lost-pet search tactics, social media strategies, and the psychology of loss, Ace—her own shelter rescue, a plucky Maltese mix who narrowly survived months wandering lost—also steps up for training. He reveals a nose for the scent of lost pets, and together they help neighbors and strangers in their searching. And in this compelling tribute to man's best friend, when Susannah suffers her own metaphorical loss of her sense of direction, it is Ace who leads her home.