Adam Whiteley, a young MP in the House of Commons working toward an equitable society, garners public support as a "White Knight." Milverton is hired by those opposed to Whiteley to oust him. William takes interest in Whiteley, and decides to test him.

Whiteley goes alone to deal with the House of Lords with the irrefutable proof obtained from Albert in hand, but finds Milverton, the king of blackmailers. Even as Whiteley negotiates with him, Milverton's devilish clutches close in on his dear brother.

Milverton blackmails Mary, exploiting her dalliance in antigovernment activities as a student. Sherlock decides to sneak into Milverton's estate to steal his evidence, but even that act was anticipated. Sherlock finds that he is not the only trespasser.