The white blanket of France's eastern Jura Mountains stretches out for 340 kilometres along the Swiss border. Trekking across this wilderness is an unforgettable journey. We follow a small group of cross-country skiers for a three-day hike through pine trees, frozen lakes, gentle slopes and sunny peaks. At night we stop off at a chalet to sample rösti, a local Jura specialty. At the Franco-Swiss border, we discover a passage where Resistance fighters and Jews risked their lives to flee occupied France between 1941 and 1945.