Triskellion Books in Order

The Triskellion books are fast, eerie adventures written for younger readers but with enough unease to grip adults too. Writing under the shared name Will Peterson, Mark Billingham and Peter Cocks follow New York twins Rachel and Adam as a summer visit to rural England turns into something much stranger.

In the first book the twins arrive in a remote village dominated by an ancient chalk symbol carved into the hillside. The locals are hostile, their grandmother is oddly distant and the landscape itself seems to hum with menace. An archaeology TV crew is digging near the triskellion symbol, unearthing something that has been protecting the community for centuries. Bees swarm where they should not, secrets are buried under the moor, and Rachel and Adam begin to realise that they themselves are tied to the mystery they’re trying to solve.

The second book widens the world. After the revelations in the village, the twins are taken in by a research organisation that promises safety and answers. Instead they find locked doors, surveillance and experiments that treat them as subjects rather than children. Escaping across Europe, they race through cities and deserts while being hunted by both their former “protectors” and fanatics obsessed with the power of the triskellion shards.

By the time of the final volume, Rachel and Adam have become fugitives. Clues left by their grandmother send them far from England to a secretive facility in the American southwest, where the last piece of the symbol may be hidden. Along the way they learn more about their parents, the true purpose of the triskellion artefacts and the cost of the abilities they are beginning to develop.

Across the trilogy you can expect chases, coded messages, underground chambers and a steady drip of paranormal elements, all rooted in a believable sibling relationship. The tone is tense but not bleak, mixing archaeological puzzles with modern conspiracy and a sense of kids having to work out who, if anyone, they can trust.

Read in order, the series moves from a contained village mystery to a globe‑spanning story without losing sight of Rachel and Adam as ordinary teenagers thrown into extraordinary danger.