As so often, the film simplifies and slightly alters the story as told in the book of the same name and written by Heinrich Harrer; Brad Pitt plays the role excellently, by the way.
Harrer, a rather egoistic young Alpinist from Austria, is in the Himalayas when Britain declares war in 1939. He is interned in British-ruled India as an enemy alien (NB: NOT for any other reason). After several failed attempts at escape in the succeeding two years, he gets away, eventually linking up with a fellow Austrian climber. In order to avoid recapture, they trek high into the mountains and head for Tibet, then closed to all foreigners. By bending and breaking the rules, they get into Lhasa, the Holy City and are tolerated. Indeed, a young educated "civil servant" assists them and continues to do so after he is promoted to high ministerial rank. Harrer builds roads and becomes tutor to the young Dalai Lama, who lives in the Potala Palace high above the city. Harrer's friend marries a local lady; Harrer himself changes to a less egoistic person over time.
After WW2 grinds to its dreadful end, Harrer stays on until the Chinese invasion of 1949. He then returns to Austria, to find that his son (born after he left Austria) has almost grown up. The films ends with Harrer, back in the Austrian Alps, reconciled with his son and his climbing and escaping friend.
This film is largely true to the book. It was badly mauled on release in 1997 because the newspaper critics wanted the standard Spielberg-style Hollywood anti-Nazi propaganda message spelt out; this film is not a propagandistic film, thank God. The blanket condemnation of the critics really showed that there is a kind of "claque" at work in the UK and USA. In fact, Brad Pitt is stellar here, his performance just right. The film is heartwarming and never boring, which shows that Hollywood can do it, when allowed.