In 1640s England, King Charles I (Alec Guinness) is engaged in a power struggle with Parliament, and civil war seems imminent to House of Commons member Oliver Cromwell (Richard Harris), who's preparing to depart for the American colonies. When he's asked to stay to fight for the Parliamentary cause, however, Cromwell agrees and proves himself a brilliant leader of the Roundhead army. Soon, it's up to him to lead his army to victory over the king's Cavaliers and take back England for the people.