The Riddle of Penncroft FarmPaperback, 1 August 2001

Lars Olafson moves with his parents to the old family farm near Valley Forge, Pennsylvania, to live with his aged aunt Cass. Lars is miserable--until he meets Geordie, a ghost whose stories of the Revolutionary War are as exciting as those of an eyewitness. When Aunt Cass dies suddenly, Lars is faced with a mystery linked to the Revolutionary War--and Geordi's ghostly stories are his only chance of solving it.