Scotland at the dawn of the 15th century was a wretched spectacle. While the feeble Robert III still clung to his throne, his kingdom rang with the sound of conflict as his son and brother grappled for power.   Sir James Douglas of Aberdour, married as he was to the King's illegitimate sister, had to tread a hazardous path through the warring factions. But having a conscience made life harder still. For in those days - and in that company - a conscience could cost a man dear...   'Through his imaginative dialogue, he provides a voice for Scotland's heroes' Scotland on Sunday