For 40 years, Alex Macdonald has stalked the hills and glens above Fort William, as did his father, grandfather and great-grandfather before him. Now he wants to hand his expertise onto a fifth generation - his 15-year-old son. In this intimate portrait of a unique way of life, we follow Alex through the ferocity of one of Scotland's worst winters to the high heat of summer, as he manages the 3,000 red deer that populate the Achnacarry estate.