1940. Britain is at war with Nazi Germany.
Eleven-year-old Eric spends his days at the place that makes him most happy: London Zoo. And there's one animal in particular he loves: Gertrude the gorilla.
With bombs falling all over London, Eric must rescue Gertrude.
Together with his 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...