Each year, the red knot, a small shorebird that winters on the southern tip of South America, embarks on a 10,000-mile journey to its nesting grounds in the Arctic. The pocket-sized long distance traveler times its migration precisely to coincide with the annual spawning of one of the Earth's most ancient creatures, the horseshoe crab, in the Delaware Bay. The eggs of the crab fuel the birds on one of the longest migrations on earth. But humans have harvested the horseshoe crab for fishing bait, and use its blood for medical purposes. With the crabs now in decline, the red knot is in danger. This story is a compelling example of how every species is interconnected, and of our potential to destroy those connections -- or restore them.