Two new students arrive with a bad case of sibling rivalry - cockapoo Maggie, and German shepherd Cody. Escorted by later-in-life lovebirds, Diane and John, the couple have grown tired of Maggie’s ‘diva’ ways. First, the trainers must unlock the mystery of why she really hates her baby brother. Meanwhile, muzzled collie, Marvin, has left owners, Laura and Dave, at their wits’ end. Concerned by Marvin’s lunging and nipping, they fear he’ll bite someone and have to be put down. As trainer Jo begins the delicate process of earning Marvin’s trust, there’s no knowing how he’ll react.