In 2003, the entire power grid of the northeastern United States and Canada collapsed — 55 million people lost electricity — because a software alarm silently crashed and nobody noticed for over an hour. We dig into how a race condition bug in a control room program created a cascading blackout that stopped subway trains mid-tunnel, trapped people in elevators, and cost an estimated $6 billion. It's the story of how one quiet software failure became the largest blackout in North American history.