Black Fox of Lorne — Marguerite de Angeli

Set in 1005 AD, twins Brus and Jan go a-Viking with their father Harald Redbeard and all their household. They plan to settle in England with Danish relatives there. But, their ships are caught in a fierce gale on the North Sea, and they are taken far off course to the western shore of Scotland. Held captive by a cunning Scottish Laird, Jan and Brus must navigate the political intrigue of chieftain, clan, and king without the help of their father, who has been killed and their mother, who is believed lost at sea. They follow adventure after adventure until they earn their freedom and find a home in Scotland at last.