The Brighton to London line. The 7:44 am train. Cars packed with commuters. One woman occupies her time observing the people around her. Opposite, a girl puts on her make-up. Across the aisle, a husband strokes his wife's hand. Further along, another woman flicks through a glossy magazine. Then, abruptly, everything changes: a man collapses, the train is stopped, and an ambulance is called. For at least three passengers on the 7:44 on that particular morning, life will never be the same again.