Thunder loves her life by Sage's side--together, they make the paw-fect pack! But when Sage invites a foster dog named Byron into their den, suddenly things get a lot more complicated. Byron doesn't seem to know the pack rules--he's sleeping in Thunder's bed, eating out of her bowl, playing with her toys, and is even stealing love from her human! Will Thunder find a way to get along with this unwelcome guest? And can she maybe, just maybe, call him friend?