In sunshine the old deserted house is a friendly landmark, and Gail even uses a shed on its grounds as a secret haven where she can write her poems. But by moonlight the house becomes eerie and terrifying. One night as Gail walks past it, a sudden sharp sound of knocking makes her whirl around. Someone seems to be trying to catch her attention, yet there is nothing but moonlit lawns and ghostly white walls to be seen. Where did that knocking sound have come from? And the weird voices -- whose can they be? When Gail wakes the next morning, she jumps out of bed. It is Saturday and she plans to do some writing. Then suddenly she remembers. Perhaps she shouldn't use the old shed as her secret room after hearing those noises and voices the night before... The highly original and intriguing explanation of this mystery leads Gail and her friend, Conan, to the solution of a series of robberies as well. A picturesque New England setting and some unusually attractive and believable characters make this suspenseful story one of Mrs. Jane's best.