North Point Cabin Mystery and Mystery of Gaither Cove by Capwell Wyckoff

The North Point Cabin Mystery and The Mystery at Gaither Cove were published by A. L. Burt in 1932.  The books were later reprinted by Saalfield.

In The North Point Cabin Mystery, Lance, Tim, and Brad stay in a cabin on Desolate Lake.  They learn about a mail carrier who was accused of a theft several years before.  The mail carrier vanished, so everyone believes him to be guilty.  The boys uncover a clue that reveals that the mail carrier had been abducted.  The boys search for additional clues in hopes of solving the mystery.

This is a very good book.

In The Mystery of Gaither Cove, Ken, Brent, and Laurie travel across country by automobile to visit their old friend, Ted, who now lives in the Ozark Mountains of Arkansas.  The four boys go on a camping trip near a cabin where a strange old man lives.  The man lights a lantern each night while he hides nearby watching his cabin.  The man is generally believed to be superstitious, but the boys feel that there is another explanation.  Meanwhile, Dana, a chicken thief encountered by the boys as they traveled to Arkansas, is staying in the woods near them.  The boys try to capture Dana as they investigate the strange old man who lights the lantern.

This is also a very good book.