In My Brother Sam Is Dead, sometimes deceit just comes in the form of little white lies. Remember how Tim tells his dad he's helping Jerry when he's actually visiting Sam? That time, no one gets hurt. But sometimes they're big, huge, stab-your-fellow-soldier-in-the-back lies. When those two Continental soldiers say that Sam was the real cow-thief, that's quite a whopper. And it has really big consequences. There are all sorts of lies in this book, and all this deceit has Tim wondering: how does he figure out who is lying and who is telling the truth?
Lying is just plain wrong. The book argues that lying can get innocent people killed, so you should never ever do it.
Sometimes lying is necessary. The book argues that there are times when you need to lie, and that's okay.