Investigates Somerled of Argyll's emergence in the forefront of the Gaelic-Norse aristocracy of the western seaboard, his part in Gaeldom's challenge to the Canmore kings of Scots, his war on the Manx king of the Isles, his importance for the church on Iona, and his invasion of the Clyde which was cut short by his death at Renfrew in 1164.