[1][2] The Sound of Thunder describes the progress of the Second Boer War through Sean's own actions, first in harrowing missions in the front lines for the British Guides, then as the leader of a commando designed to fight the Boers on their own terms – guerrilla combat in the veld.

Sean and his son Dirk finally leave the wilderness and discover that a war is brewing between the English and the Boers.

The commander of the Boers is Sean's brother-in-law, Jan-Paulus Leroux, brother of Katrina who died in When the Lion Feeds.

The peace which follows finds Sean with hopes of marriage, settling down to develop new land by planting wattle.

The book ends with Sean's brother Garrick forgiving him and Dirk running away, promising to ruin the Courtneys.