In 1776 on the eve of the American War of Independence Charles George MacPherson, a patriotic young American, flees the Mohawk Valley in New York after killing a well-known Loyalist.

He travels to Paris and later to London where he discovers friendships among the people he had presumed to be the enemy, only gradually resolving his conflicting loyalties.

At the heart of his dilemma is his life-long love for the beautiful Mary Graham and his developing friendship with Thomas Graham, her devoted husband and Perthshire laird. But his past from the Mohawk Valley catches up with him and has to be confronted amid the horror of London during the anti-Catholic Gordon Riots.

"Lion of Barossa" takes forward the story of the young American Charles George MacPherson and his friends Thomas and Mary Graham.

After the Gordon Riots in London Charles travels with his friends to Portugal and Spain before returning to America, where he finds wealth and unexpected, but fleeting, happiness. He is then summoned to France where Mary Graham is seriously ill. After her death the two friends are caught up in the horrors of the French revolutionary Terror and Thomas decides to take a hand in the war by raising his own regiment. Eventually overcoming official opposition, Thomas at last achieves a permanent commission and at Barossa becomes a hero in his own right.