It's the late summer of 1642. In England there is war: on the one side, Charles I, the King, defending what he believes his divine right to rule by prerogative, and the Parliament, led by the Puritans, which rejects what it believes is a despotism intended to suppress the traditional rights and liberties of Englishmen.

Into this maelstrom steps Edmund Holyfen: The eldest of three sons of a decaying armigerous family from the fen-country of East Anglia, he arrives from America, to which he stowed away in 1630 and where his wife and son were kidnapped, tortured and murdered by the Pequots. Edmund's father, Sir George, lives with Thomas, his youngest brother, in a crumbling rectory in the village of Holyfen, on the Great Ouse between St Ives and Ely. His mother lives in Huntingdon, a house on the High Street purchased from her brother, the Member of Parliament for Cambridge, Oliver Cromwell. Cromwell, aware of Edmund's experience in the wars against the Pequots, enlists him for service against the King: seizing the plate of Cambridge's universities and the arms of Cambridge Castle.

Sydney, a merchant in London,  is the middle Holyfen brother. He's close to John Hampden, his uncle and a long-time leader of the Parliament's opposition to Charles who is raising a regiment to do battle with the King's forces. Sydney, who is connected to the more radical elements of the Puritan movement, also edits a publishes a newsbook, Anglia Rediviva, and employs the firm's apprentices in gathering news, to the considerable wrath of his nominal boss, Ralph Halpenny.

By the beginning of September, King Charles has declared war against Parliament and is mustering forces in Nottingham. Cromwell and Edmund are raising a troop of horse among the Puritans of East Anglia. Hampden's regiment, supplied with guns and butter by Sydney's efforts, have joined the muster of Parliament's army in Northhampton.

By late September, the King's army, with the horse commanded by his son-in-law Prince Rupert, have departed Nottingham for Shrewsbury. Sydney is being sued for breach of contract by Ralph Holyfen, and has been enlisted by John Hampden to assist in negotiations with the Scots. Cromwell's troop of horse is preparing to depart East Anglia to join the main army of Parliament commanded by Essex, which is marching on Worcester. Rupert routs the Parliamentary Horse in their initial encounter at Powick Bridge.

The troop raised by Cromwell joins Essex at the end of September, while William Firth, Sydney's apprentice, develops a friendship with Boy, Rupert's dog. The armies joust for position -- during the course of which, Cromwell encounters a disguised Rupert -- and finally collide in near Kineton in Warwickshire, the battle known as Edgehill.