The Secret in the Old Well — Carolyn Keene

When Arlene Sherwood disappears, the Danas' only clue is that Arlene received a dire prediction from a psychic reader. Did Arlene run away out of fear caused by the prediction, or is something far more sinister at play? Jean and Louise believe that Arlene has been abducted, especially after they learn that Arlene's father has also disappeared.

Mrs. Sherwood soon receives a message from her husband, requesting that she place certain important drawings in an old well. The drawings are very valuable to Mr. Sherwood's work, and the loss of the drawings will be a great blow.

The girls deduce the location of the well and plan to substitute fake papers. Their plans fail, leaving the girls in a dangerous position as they continue their search for their missing friend and her father.