If there's one thing Derek has learned from comic books, it's that everybody has a weakness, something that can totally ruin their day without fail. For the wolf man it's a silver bullet. For Superman it's Kryptonite. For Derek it's a letter. With one letter, his dad is sent back to Afghanistan to fly Apache helicopters for the U.S. Army. Now all Derek has are his dad's letters. Ninety-one of them to be exact. He keeps them in his old plastic lunchbox, the one with the cool black car on it that says Knight Rider underneath. Apart from his comic books, his dad's letters are the only things he reads more than once. He knows which ones to read when he's down and needs a pick-me-up. He knows which ones will make him feel like he can conquer the world. He also knows exactly where to go when he forgets Mom's birthday. No matter what, each letter always says exactly what he needs to hear. But what he wants to hear the most is that his dad is coming home.