In 1796, impetuous Martha Morgan becomes the mistress of the struggling Plas Ingli estate, at only eighteen years old. Though she loves her husband David dearly, she is desperately lonely in a strange house, and her quick wit and cutting humour make her as many enemies as friends. There are mysteries surrounding the great fire that devastated the estate but Martha's questions about it remain unanswered. Nobody else seems to realize that their haughty servant Moses Lloyd, the disinherited son of the local squire, is not as trustworthy as Martha's husband hopes. The local gentry think that she is far too clever for her own good and indeed it seems inevitable that Martha will fall into their trap which is designed to send her to the gallows. How can she possibly escape? "On Angel Mountain" is a gripping tale in the tradition of Winston Graham's Poldark.