An interest in ancient stone circles keeps James, a financial trader in the City of London, well grounded. When visiting a little-known stone circle in North Wales, on the summer solstice, he is transported back to the time of the circle's construction. James lives amongst the Late Bronze Age villagers, befriending the architect of the stone circle, Barnaby, and a young widow called Eira. James rejoins the present, quickly realising he was far happier in the past than in his current, shallow London life. He returns to the past only to find it under siege by the Hunllef, a warring, wandering tribe. Following a bloody battle he and Eira escape to the present. Beth, a PhD student studying the history of stone circles, befriends James and Eira and becomes entangled in their lives spanning two time zones.