When fourteen-year-old Gem loses her heirloom necklace at her new boarding school in Eastbourne, friends Lana and Nooshi help her to find it, but in doing so, discover that a strange girl called Ember and school archaeologist, Cessi, have the exact same necklaces. Sinister things begin to occur as Cessi and the girls investigate what the necklaces signify; discovering links to Sir Arthur Conan Doyle and rumours of an alien tracking device.
When the girls finally learn the Earth-shattering truth, the question is, should they reveal it and would anyone believe them anyway?