John à Cleeve of Cleeve Court in Devon is educated at seminary school in Douai in northern France, but loses his faith and decides to follow his cousin, Richard Montgomery of Ireland, in a military career. An ensigncy is obtained for him by his elder brother in the 46th Regiment of Foot. He is transported to Halifax, Nova Scotia, where he is reunited with Montgomery, who is serving in the 17th Regiment of Foot. Both regiments are intended by Pitt for the British conquest of New France on the St. Lawrence River.
The 17th Regiment takes part in the capture of Louisbourg on Hudson Bay. The 46th, under General James Abercromby, attack Fort Carillon, between Lake George and Lake Champlain, but are rebuffed with heavy losses, with John à Cleeve as one of the captured wounded. A transport under Sergeant Barboux and the Ojibway (or Ojibwas) chief Menehwehna carry the wounded flotilla down the Richelieu River, but as Barboux has a secret message for the military in Quebec and Montreal he decides on a short cut, directed by Bateese Guyon, over the Adirondack mountains. On a high pass the party are attacked by Iroquois Indians, allies of the British, and discover that another party had already been attacked. This party included Armand des Noel-Tilly of Boisveyrac. Bateese Guyon retreats but Barboux, Menehwehna and à Cleeve continue, the latter two finally making it to Fort Amity.
At the fort John à Cleeve, a fluent French speaker, is accepted as a wounded Frenchman from Fort Carillon and Diane des Noel-Tilly, daughter of the commander, falls in love with him. His disguise is eventually penetrated and after revealing his true identity to Diane he escapes with Menehwehna to Ojibway territory on Lake Huron. She rejects but does not betray him.
After having spent nearly two years with the Ojibwas, John à Cleeve hears of the British advances to Quebec from the north-east and Fort Amity from the south-west. He returns in time to rescue Diane during the British and Indian assault on the fort. Still dressed as an Ojibwas he proceeds to Montreal, which is in the process of falling to the British. He encounters Richard Montgomery, now an adjutant in the 17th Regiment. Following the fall of Montreal on the 8th September, 1760, John à Cleeve decides to join the British administration in Canada. Richard Montgomery finally ends up in New York where he marries into the distinguished Livingstone family and becomes a Brigadier-General in the army of Congress.
In December 1775, John à Cleeve is Superintendent of the Works in Quebec, a position held under the British Crown, and Richard Montgomery is a commander of Congress forces advancing on the city following the commencement of the American War of Independence (1775-83). They confront each other at the Près-de-Ville, on the rover entrance to Quebec. During the assault by American forces, under cover of a snowstorm, Montgomery is killed, with the body later being identified by à Cleeve and removed to a mortuary in St. Louis Street. Outside of the mortuary John à Cleeve and Diane des Noel-Tilly meet and are reconciled. They marry and settle at Boisveyrac but retain contact with the Ojibwas Indians of Lake Huron.
In 1818, the remains of Richard Montgomery are removed from Quebec to the cenotaph in New York, with part of the journey overseen by the widow. The families of Schuyler and Livingstone, which had cheered the advance of the British to Fort Carillon in 1758, stand in silence as Montgomery’s remains pass down the Hudson River.
The last short section of the novel relates to the hundred year celebration of the defeat of the Americans at Près-de-Ville. The ballroom at the Citadel has on display the sword of Richard Montgomery and the dress of Sergeant Hugh McQuarters, a hero of the Près-de-Ville, who had previously fought with the British at Fort Carillon.