The Scottish Prisoner

In 1760, Jamie Fraser is a paroled Jacobite prisoner of war living in England's Lake District, barred from claiming the son he cannot publicly acknowledge. Lord John Grey, a British army officer who has every reason to avoid him, arrives with a coded letter that only Jamie can translate.

The letter points to a corrupt officer named Siverly and to a conspiracy brewing among Irish Jacobites, and Jamie and Lord John are pushed into an uneasy journey together that leads from London toward Ireland. Their quarrel of a year earlier hangs over every mile, and neither man wants the other's company.

The Scottish Prisoner is the third novel in Diana Gabaldon's Lord John Grey series, which follows the Seven Years' War-era soldier and sometime sleuth, and it crosses over closely with her Outlander books through Jamie Fraser. Reviewers describe it as part historical mystery, part adventure, with the relationship between the two leads carrying more of the story than the plot does. It leans on knowledge of earlier books in both series.