Wealthy and precocious teenager Juliet transfers from England to New Zealand with her family, and soon befriends the quiet, brooding Pauline through their shared love of fantasy and literature. When their parents begin to suspect that their increasingly intense and obsessive bond is becoming unhealthy, the girls hatch a dark plan for those who threaten to keep them apart.

As the Christmas holidays begin, a group of 10 war-obsessed kids have a wave of inspiration: What if they spend the next two weeks engaged in a simulated war, armed only with shields, wooden swords, snowballs, and a fierce sense of competition? With a bounty chest waiting for the winners, the two sides gradually grow in size, and the war grows in importance, taking over all aspects of their lives.