The author calls this a religious parable and it is called an allegory in the book itself. A young, 18th century Scottish boy is converted to strict Calvinist theology, strives for assurance of his salvation as an elect person, eventually confirmed for him by his hyper-strict, hyper-fundamentalist pastor and mentor. Assured that no sin can affect his salvation and election, he comes under the influence of a strange, manipulative, controlling presence . - Summary by Dean McIntyre