Act I, Tableau 1. In MacGregor's castle, Mary, who in her heart really loves William, is being wed to Douglas. The guests celebrate the wedding. MacGregor blesses the couple. Margaret intones a portentous song with the line "Why is your sword so red with blood, Edward"? This disturbs Douglas, and Mary tries to calm him. He tells about being attacked on the road by highwaymen. Mary faints, but soon recovers. Douglas continues by telling of a mysterious man who rescued him. MacGregor sends Mary and the guests away to the banquet hall. He reveals to Douglas the details of Mary's previous two suitors.