It's 1216, just one year after the battle at Rochester Castle, and a new enemy threatens English life that's far more terrifying than King John - bands of Celtic raiders, stealing livestock and killing anyone who gets in their way. After the death of their father at the hands of these raiders, siblings Hubert, Blanche and Kate and their cousin Guy are determined to defeat them.

A ragtag group of Knights Templar hold out for months against the hard-fought siege of Rochester Castle in the thirteenth Century. Set in the time of King John's signing of the Magna Carta treaty, the group struggles against the king to defend the freedom of their country.