One evening, a team of scientists realise that a tracking device they'd attached to a bull shark off the coast of NSW has come ashore and is now leaving a GPS trail all over Wollongong and surrounds. This tag, once attached to a bull shark's dorsal fin, contains valuable scientific data that could help unlock the secrets of the deep, and of the apex predators who call it home. But will a team of researchers, citizen scientists and a social media frenzy be enough to track down a lost shark tag before the signal goes dead?