It is August 1914 and World War I has just begun. Lieutenant Harry Colebourn (Michael Fassbender), a veterinarian with the 34th Fort Garry Horse Division, is on his way from his home in Winnipeg when he buys a bear cub. When Harry's regiment is sent to fight in France, the young vet knows Winnie cannot go any further. He finds a home for her at the London Zoo, and promises to return as soon as the war is over. Soon she is the star attraction at the zoo. She delights and comforts the children whose lives have been torn apart by war and ultimately she inspires the stories of A. A. Milne through which she lives on forever.