Christmas 1669. In the grip of the coldest winter for years the River Thames is frozen from bank to bank & London celebrates with a traditional frost fair held on its broad back. Revellers come from far & wide to enjoy the spectacle. Among the throng is ambitious young architect Christopher Redmayne. By chance he meets a good friend Constable Jonathan Bale attending with his family. As the adults talk Bale s sons skate around them. But their competitive nature spells trouble onto thin ice & is in danger of crashing into the freezing water below. Christopher & Jonathan save the boy but make a chilling discovery the frozen corpse of a naked man embedded in the ice. Bale vows to investigate but Christopher sees no reason to involve himself further until his own brother Henry is accused of the murder & thrown in jail. Now Henry faces execution if Christopher cannot prove his innocence. The architect must risk all he holds dear both professionally & personally to uncover the truth.