What is the poem 'Jessie Cameron' about?

Jessie Cameron is a poem about the story of a girl who is propositioned by a young man but rejects him. The young man is the son of a "witch" and referred to as being of gypsy descent. Jessie is an outspoken girl, and turns this man down even after he tells her of his undying love for her on the basis that "he may be right for others" but not for her. The poem ends tragically- both Jessie and her lover disappear into the sea and cries are heard as echoes forever more. Nobody knows whether the young man threw his life away or whether he lost it... hints at his sorcerous background.