When Fresno City College professor David Durfee signs on for a medical mission to Uganda, despairing over the recent loss of his wife and son, he seeks only escape, but receives more than he bargained for. In Uganda, while exploring nearby Bwindi Impenetrable Forest, Durfee encounters a fearsome silverback mountain gorilla, known to local game trackers as "The Old One." Despite a terrifying beginning, an unlikely friendship develops between the two. They meet in the forest daily, and Durfee teaches his rafiki (friend) to communicate in basic sign language. The friendship is threatened when a treacherous landlord attempts to shut down the Kisoro Mission, where Durfee stays, and when game poachers plot to kill and dismember his gorilla friend. When the medical mission ends, Durfee must decide whether to return to California and his teaching career, or to remain in Kisoro to pursue his unusual friendship with the silverback. His decision leads to tragic results. In the end, however, Durfee's experience in Uganda is life-changing.