Jeffrey and his friend Ben get to stay by themselves, without a baby-sitter, while their parents go to a party. Ben has his chemistry set out and Max, the fourth-grade ghost, is conducting experiments. What if Max's secret formula backfires?.
Jeffrey and his friends are excited to be starting fourth grade, but their pal Max, the ghost, refuses to be promoted. Will fourth grade be a disaster without him?.
Jeffrey brings his father's collection of prime 1950s baseball cards to school. At school the cards disappear and Max, the ghost is the number one suspect.
Bradford the ghost goes to school with Jeffrey and Laura when they begin fifth grade, and being both mischievous and invisible he creates a lot of problems.
Lars Olafson's move to a farm near Valley Forge brings him friendship with the ghost of an eighteenth-century ancestor who recounts his adventures during the American Revolution.