British Transport Police chase down a mysterious trespasser known as 'spiderman'. The Great Western Railway's top brass holds a naming ceremony for a new electric train, but the new route requires demolishing a 120-year-old footbridge in only 72 hours.

At Paddington, the early morning service from Swansea breaks down and causes major disruption during the morning rush hour. Meanwhile, the staff face further challenges with a string of medical emergencies at the station and sabotage on the tracks.