It is 1940 and Britain is at war with Nazi Germany. Eleven-year-old Eric spends his day at London Zoo with one animal he loves: Gertrude, the gorilla. But with bombs falling all over London, Eric must rescue Gertrude. Together with his Great-Uncle Sid, a keeper at the zoo, the three go on the run. But while hiding out at the seaside they uncover a top-secret Nazi plot. Will Eric be able to foil Hitler's plans and keep Gertrude safe at the same time?