After a transcript of a highly classified meeting is found in the hands of an enemy agent, an esteemed professor will remain the primary suspect unless a method by which the meeting could have been surreptitiously recorded is found. Truman Bradley's introduction includes demonstrations of how sound waves can force crystals out of solution and of the piezoelectric properties of quartz - interesting, but far from rationalising the highly improbable capacity of crystals to record sound (and even preserve it for thousands of years) that is central to the episode's plot. Not much happens in this simple 'spy-fi' outing, too much time is spent on the clichéd triptych of the professor, his daughter, and the handsome federal agent/doctor sent to investigate the leak, and the final scene, when the traitor explains his motives, seems forced. Not one of the better episodes of the early sci-fi anthology.