What was the mystery in Nancy Drew and the Clue Crew Scream for Ice Cream?

In "Nancy Drew and the Clue Crew: Scream for Ice Cream," Nancy and her friends investigate a mystery involving a series of strange events at the local ice cream shop. The shop's owner is facing trouble when ice cream flavors start disappearing, and a ghostly figure is rumored to haunt the place. As Nancy gathers clues and interviews witnesses, she uncovers the truth behind the spooky occurrences and resolves the mystery surrounding the ice cream shop. Ultimately, the case highlights Nancy's cleverness and teamwork with her friends.