One minute sixteen-year-old Ruby Morris is having her first proper snog with Caspar McCloud in a hot tub, and the next she's being bundled inside the house, dripping wet, cold and in her underwear. Not cool. As she and Caspar shiver in the kitchen, it starts to rain. They turn on the radio to hear panicked voices - 'It's in the rain ... it's in the rain ... '
That was two weeks ago, and now Ruby is totally alone. People weren't prepared for the rain, got caught out in it, didn't realize that you couldn't drink water from the taps either. Even a drip of rain would infect your blood, and eat you from the inside out.
Ruby knows she has to get to London to find her dad, but she just doesn't know where to start ... After rescuing all the neighbourhood dogs, Ruby sets off on a journey that will take her the length of the country - surviving in the only way she knows how.