A Catholic in Protestant Scotland, Lady Ashley is blessed to receive a Catholic priest, Mr. Welford, into her home as chaplain. Mr. Welford brings with him his ward, a young man named Anthony who had been left on his doorstep as a baby fifteen years before.

Her neighbor Lord Drummore, a zealous and fanatic Presbyterian, remembers Mr. Welford as his old schoolmate and graciously invites him and Anthony to visit his castle. An unlikely friendship begins to form between Anthony and Lord Drummore's five children, with the caveat that Anthony must never introduce the subject of religion to them.

Before the friendship has time to grow, however, an ugly change comes over Lord Drummore. Calling Anthony into his study, he angrily forbids the boy ever to set foot on the Drummore property again. Lord Drummore refuses to give any explanation for this demand, and the boy and his guardian can only surmise that Anthony must have accidentally mentioned his religion to the children.

Immediately after Anthony's dismissal, Lord Drummore becomes tyrannical towards the Catholics in his area, and he pitilessly seeks vengeance on Anthony in particular. But the boy is innocent, and no one knows why the wrath of Lord Drummore has fallen on young Anthony.