The plot in An Imperfect Spy is one of the most satisfying of the Amanda Cross novels. The book is not really hampered by trendy historical happenings that seem to date the other novels but instead focuses on real, substantive issues. It is tightly constructed and turns on its self. Cross has carefully constructed a novel with delightful twists and turns.

We first meet Harriet, who simply appears almost out of nowhere, while Kate is lecturing at the Theban School.

Eventually Harriet appears at Kate's apartment. When queried about her sudden appearance, she reveals that no one takes any notice of old women and it would have been easy to slip past the doorman but instead she simply told him she was Reed's aunt. In other words, she assumed a new identity.

She later reveals that this is not the first time she has assumed a new identity...