In 2546 the population has risen to 35 billion. All cities and transport systems are underground and vast farms cover the surface. Seven people on a train journey from the UK pass through an underground network of tubes on their way to the Himalayan Mountains. On the journey, the seven must contend with a catastrophe that will change all their lives forever. During the journey, a meteor strike in Ukraine causes widespread devastation. When the travellers reach their destination, they realise all is not well on the outside and set to work immediately to help other travellers who are arriving....