Fifth-grade narrator Ritchie Willis tells about the time in 1939 when his mother was hospitalized for a nervous breakdown, his little sister, Rosie, was sick at home with fever, and he himself was terrorized by the school bully and ignored by his cold father. Much of the responsibility for the house and Rosie fell on Ritchie's small shoulders: Every day after school he had to come straight home to look after Rosie and warm supper for his father. One day, however, he sees his reclusive cellist neighbor's dog dead on the road. He goes to tell Thad Grailowsky about his dog, and the two become friends. Ritchie confides in Mr. Grailowsky, talking to him about his mother's absence and Rosie's illness. He also tells him about Rosie's fantasy of a troll living under Mr. Grailowsky's bridge. Suddenly, letters start coming to the house for Rosie from the troll, named pod (spelled the same right side up and upside down). These letters keep Rosie's spirits up, and even Ritchie begins believing in pod's existence. Taking courage from the little troll, Ritchie faces his fears and triumphs over them. His mother comes home and Rosie gets well, but Mr. Grailowsky leaves to join the Canadian army to fight in WW II. Pod's letters become postcards from abroad and then cease entirely -- and Thad Grailowsky is reported missing in action. After the war, Rosie receives a final postcard from pod, ""We Won."" Ritchie then realizes that Mr. Grailowsky will come home one day. McKenzie's (A Bowl of Mischief, 1992, etc.) story is heartwarming, but the reader won't understand why it takes Ritchie so long to figure out the troll's achingly obvious identity.