Christmas, 1648. King Charles I is under house arrest following his defeat in the Civil War. Oliver Cromwell is plotting in Parliament. Can they bring their king to trial for treason?

Parliament races to build a bulletproof case of treason against King Charles I, as he prepares an unexpected defence that will decide the fate of a nation.

Charles I is found guilty of treason. Parliament races to get the king to the scaffold before foreign powers intervene and hurriedly passes an act preventing future succession.