Little Sister

In "Group Fifteen Files" by Mark Dawson, former SAS operative Bjorn Thorsson seeks a quiet life after leaving the military, aiming to escape the traumas of his past. However, when his sister, Gudrun, gets entangled with a hedge fund owner, Bjorn vows to help her, only to find himself caught in the crosshairs of a covert government agency with its own agenda. As he navigates the perilous streets of London and the rugged Highlands of Scotland, Bjorn must outsmart both the financier and Group Fifteen to ensure his sister's safety and his own survival.