Jill Ross, a veteran polygraph examiner, is asked to examine Peter Clayman, the new doctor in town, with whom she has already had a brief flirtation, and who may be a suspect in a murder case. Although Clayman initially passes the examination successfully, a new witness comes forward identifying him as the murderer. This time the results of the test are inconclusive. Although Ross believes Clayman is innocent a question of doubt lingers in her mind. Now Jill must decide whom to trust - her lover or herself.