Many animals can navigate by sensing the earth's magnetic field. Not humans, though. But might we have evolved the sense but forgotten how to access it? 40 years ago a British zoologist thought he had demonstrated a homing ability in humans. But his results failed to replicate in America and the research was largely discredited. But new evidence suggests that our brains can in fact detect changes in the magnetic field and may even be able to use it to navigate. Jolyon Jenkins investigates, and talks to a Pacific traditional seafarer who has learned to navigate vast distances across the ocean with no instruments, and who describes how, when all else fails, he has been able to access what he calls "the magic". Is the magic still there for all of us, just waiting to be rediscovered? Producer: Jolyon Jenkins