As many as a million spectators turn out for the Macy's Thanksgiving Day Parade. Another 200,000 show up the night before to watch the enormous balloons inflate. Keeping New York City safe on an ordinary day is challenging enough; locking down a massive parade route is all the more so. But the New York Police Department has recently deployed a new secret weapon to counter body-worn bombs: A team of Labrador retrievers who have graduated from patent-pending "Vapor Wake" security training.

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