British secret agent Susan Collis is shot whilst on a mission in Croatia, and retires to Scotland under an assumed identity of Ann Cameron to manage a sporting estate owned by a successful London businessman, Anthony Barron. Ann falls in love with Anthony and the pair marry, but her happy settled life in the Highlands and London is disrupted when she and her former colleague, Rose Armstrong, discover evidence of corruption in Ann's old department in the MOD. And when the life of Susan's former partner and close friend, Jess, is put in danger, Susan decides to return to work to uncover the truth about the numerous threats, both foreign and domestic, which imperil not only their lives, but also the security of the nation. Their investigation identifies a criminal in the MOD and a double agent within MI6 whose threats are removed.