Charley claims to have discovered the third level of Grand Central Station in New York, which authorities deny exists. His psychiatrist friend, Sam, dismisses it as imagination but later disappears. Charley finds an old letter from Sam, postmarked 1894, describing the third level as real and inviting Charley to visit. The most mysterious part is that Sam was Charley's psychiatrist who had previously been skeptical of the third level's existence.