Peter Pentecost, a young monastic scholar, is informed by shadowy figures who are plotting to depose the king that he is the legitimate son of the deceased Duke of Buckingham and that, as the last of the Bohun line, he has a claim to the English throne.

They introduce him to the lore of the countryside, and reveal the existence of a self-contained outlaw society, invisible to the agents of the state, with its own system of communication and intelligence gathering.

As the novel progresses, Peter has increasing doubts about the venture he is being asked to undertake, and the motives of those behind it: "They claimed to stand for the elder England and its rights, and the old Church, but at their heart they stood only for themselves."

(Macbeth, Act 1, Scene 5) David Daniell in The Interpreter's House (1975) quotes Kipling who professed to be "rested and delighted" by the book and who called it a tour de force.

[3] David Goldie noted in 2009 that "One of the animating ideas of The Blanket of the Dark is that English values are expressed more profoundly in the quiet wisdom of its folk than in the forceful actions of its rulers".