In the book Eye Of The Needle, how does Follett demonstrate good vs. evil in the characters of Lucy, David, and Faber?

In Follett's
thriller about a German spy in World War II England, he introduces complex characters and a good
vs. evil struggle on several levels within and between Lucy, David and Faber.

Lucy and David, the married couple inhabiting the small island Faber hides out on, have
had marital problems since David's legs were lost in a car accident.  Lucy is lonely and feels
estranged from her husband, and has an affair with Faber, not knowing he is a German spy.  She
feels guilty and still loves her husband, and after his murder tries to stop Faber from carrying
out his mission.  In this way Lucy also represents "good" on the British side vs.
"evil" on the part of the ruthless and manipulative German spy.

David wishes he was a better husband and that he felt more complete, he just doesn't
know how to be.  He finds out about the affair, the "good" husband betrayed and
seeking revenge, but is killed in the process, he too being defined as the good British citizen
against the evil german spy.

Finally there is Faber himself, who is
"good" in the sense he is loyal to and fighting for his country, actually loves Lucy
(which is why he doesn't kill her) and in the end, transmits faulty information to his
government about the allied invasion force.  Yet he knowingly has an affair, manipulates Lucy
and kills her husband while spying for Nazi Germany.