What is the theme in Loitering with Intent by Muriel Spark?

Evil and manipulation is a central theme in this book. The primary sources of evil in this story are Sir Quentin and Warrender Chase, who both seem to have a knack for professing it. Fleur begins to suspect Sir Quentin's evil ways, and her suspicions prove to be correct when she discovers how he is manipulating the members of his Association. The evil and manipulation in the novel seem to go together: the main evil stems from the leaders of the groups who then manipulate their followers.