This is the story of the Monterey Bay Aquarium’s 501st attempt to save a stranded orphan otter. From her discovery as a newborn pup crying on the beach, through her rehabilitation in secret roof tanks atop the Monterey Bay Aquarium, follow Otter 501 as she learns how to survive in the wild. Watch as she is introduced to her surrogate mother — a method invented by marine biologist Karl Mayer and his team in 2005 — and follow as she struggles to learn how to dive, hunt, eat, and fend for herself in an artificial environment meant to mimic the “real world.” It is a tale of mysterious threats, persistent failures and small victories, where survival is a long shot at best. Throughout, Otter 501 acts as a lens. Her story reveals a previously unseen world of otter behavior and also acts to illuminate some of the most difficult ecological questions of our time: Do we have a responsibility to save species that hover on the edge? Are our actions the cause of the illnesses sweeping through the sea otter population? And since we simply can’t return the world to its pristine pre-human form, are preservation efforts like this doomed to fail? Otter 501’s survival may hold the hint of an answer.