What do you infer from Sam’s letter to Charley?

Explanation

The way Charley came across Sam’s letter was surrounded in mystery. Among his oldest first-day covers, he found an envelope. The envelope containing the letter bore the
address of his grandfather. It was written on July 18, 1894. The postmark showed the Picture of President Garfield. Generally the first day covers have blank papers in them, but this one contained a letter. The letter was addressed to Charley. In the letter Sam had informed Charley that he was living on the third level. He had also told Charley and his wife to keep looking for the third level. Clearly, the letter was a product of Charley’s imagination