High in the Swiss Alps, the Bernina Express climbs over 2,000 meters through sub-zero mountain passes without the help of a cog wheel, making it one of the steepest adhesion railways in the world. This episode of Mighty Trains follows the people who keep it running: conductors, a driver with four decades on the line, trackmasters who clear ice from tunnels with pickaxes, and avalanche teams who use dynamite to bring down snow before it can bury the tracks on its own schedule. The film moves between cab footage of the spiral viaducts and rock cliffs the line was blasted through and interviews explaining how Swiss engineers solved the gradient problem without cog rails. Heavy snowfalls, ice buildup, and avalanche risk are treated as daily operational hazards rather than rare emergencies, and the UNESCO-listed route's history gets folded in alongside the present-day maintenance work needed to keep a century-old railway running through weather that regularly hits 200km/h winds.