The Murder at Sea Haven Beach

What is the real reason Dr. Thomas Erickson engages Leigh McCarthy to work undercover as a substitute teacher at Sea Haven High School? There are certainly problems at the school, discontent and discord among the faculty are some of them, but are they serious enough to warrant spying on the teachers, and why doesn’t Dr. Erickson trust the principal of Sea Haven High School to solve the problems in his own school?
Leigh cooperates with Dr. Erickson until one of the faculty, handsome, arrogant, and narcissistic Robert Gerding, is murdered.
She discovers that there are others besides a few teachers who had an interest in seeing Gerding dead, and although she is not a professional investigator, she sets about interviewing those other people who may have wished the worst for him.
What she also discovers is that nothing is what it seems to be.