Luna has always wanted to be a therapy dog at Therapy Dogs Worldwide. Now she's a whisker away from reaching her fifty-visit pin that will make it official. But when her "clients"--the children who visit her--are put into a therapy group, Luna's routine is upended. Like the moon, Luna shows different faces at different times. And her clients each have different needs--Beatrice is tangled in knots of anger, Caleb rushes like a waterfall, Amelia carries fear heavy like a shadow, and Hector is quiet as a rock. To comfort the kids, Luna can be what they need her to be, but can she be everything to them all at once? When Hector doesn't show up to a session one day, the kids set off on an unexpected quest to find him. Luna joins to keep them safe, and they must work together to learn the truth.