After being forced to give up his pet fox Pax, a young boy named Peter decides to leave home and get his best friend back. Pax and Peter have been inseparable ever since Peter rescued him as a kit. But one day the unimaginable happens: Peter's dad enlists in the military and makes him return the fox to the wild. At his grandfather's house three hundred miles away from home, Peter knows he isn't where he should be - with Pax. He strikes out on his own despite the encroaching war, spurred by love, loyalty, and grief, to be reunited with his fox. Meanwhile Pax, steadfastly waiting for his boy, embarks on adventures and discoveries of his own ... From bestselling and award-winning author Sara Pennypacker comes a beautifully wrought, utterly compelling novel about the essential truths that define us and the devastating costs of war. Pax is destined to become a beloved classic. -- from inside cover.

It has been a year since newly orphaned Peter and his pet fox Pax, now a protective father, have seen each other, but their paths cross again when Pax's kit falls desperately ill forcing him to turn to the one human he knows he can trust.