Balthazar Jones has lived in the Tower of London with his loving wife, Hebe, and his pet, the oldest living tortoise, for the past eight years. That's right, he is a Beefeater. It's no easy job navigating the trials and tribulations that come with living and working in the largest tourist attraction in London. The once white-hot flame of Hebe and Balthazar's love has been snuffed in the few years since their son Milo died, a death for which Balthazar blames himself. When Balthazar is tasked with setting up an elaborate menagerie within the Tower walls to house the many exotic animals gifted to the Queen by foreign dignitaries, life at the Tower gets all the more interesting. Penguins escape, a bearded pig goes missing, giraffes are stolen, the komodo dragon sends innocent people running for their lives, and canaries suffer fainting fits. As he attempts to cope with this four-legged invasion and his marriage continues to crumble, Balthazar must confront the secret he has been harbouring about his son's death, if he wants to save his marriage and his sanity.