Eighteen-year-old Julia and twelve-year-old Alex are just like many other brothers and sisters. They fight ." a lot." Yet something is different in this family. Alex believes his sister has an evil mission-to ruin his life.
One day, Julia backs over Alex's shiny new bike, yet Alex is the one who is punished by his parents for leaving his bike in the driveway. Outraged, Alex officially declares "war" on his sister. He is tired of her unforgiving, cruel, and rude nature and soon discovers the best way to get revenge. Alex finds precisely the right moment and reads a page from Julia's diary over the intercom at school. Julia is mortified, but Alex still isn't satisfied. He finally has his chance for the ultimate vengeance when his parents depart for a trip to France and leave the two children home with no adult supervision. Alex waits for the perfect moment and makes a desperate and dangerous move as he attempts to get even with his sister one last time.
But in the end, Alex could end up hurting many more people than just his older sister with his crude war plan .