Daisy, a teenager from New York, is sent to the English countryside for the summer to stay with her step-cousins. She soon immerses herself into her new life - made all the more easy when she falls for the sexy, thoughtful Eddie - until their perfect summer is blown apart by the sudden outbreak of a terrifying nuclear war. Along with Eddie's younger siblings, Isaac and Piper, they are left in isolation and forced to fend for themselves. When they are violently separated Daisy must embark on a perilous journey in order to be reunited with the boy she loves. Eddie is never far from Daisy's mind, but as her journey to find him becomes more desperate, the idea of what she may or may not find consumes her consciousness and haunts her soul.