Harriet the hippo is captured by Roman soldiers, to be taken back to Rome. She discovers that a baboon friend named Boon has also been captured. When the Romans take a detour to Jerusalem, Harriet and Boon escape. They end up in Bethlehem at the time when the wise men came to see Jesus. News of Herod's plans to kill the baby force everyone to leave quickly. When Joseph takes Mary and Jesus to Egypt, Boon and Harriet realise that they can get home by following them."