This episode focuses on the treatment of sporting enthusiasts who've been injured on two wheels. Nineteen-year-old Billy has been thrown 20 feet from his motocross bike during a race, suffering multiple spinal injuries, and he's lost sensation from the chest down. He's been transferred from a hospital in Brighton to St George's for treatment by the specialist neurosurgical team. Billy's parents and brothers witnessed his crash and are by his bedside, braced for the worst. Meanwhile, 53-year-old teacher Dave has facial injuries after riding his new bicycle into the back of a stationary car in Richmond Park. The crash is a wake-up call for Dave. 'It makes you realise you are quite vulnerable,' he says. 'Maybe I'll go back to golf and fishing!' And 30-year-old adrenaline junkie and ex-Royal Marine Richard has badly dislocated his thumb after falling off a bicycle. As the emergency team try to realign the tip of his thumb, Richard enjoys the effects of the pain-killing gas and air while reflecting on his time in the marines and the evolutionary benefits of risk.