What Could Go Wrong?

When cousins Gracie, Charlie and Ed die are invited to fly to San Francisco to visit their Aunt Molly, Gracie's mother decides they may go, musing ``What could go wrong?'' If only she had known about the man in the Ha waiian shirt carrying a newspaper with a mysterious code written on it. Or about the bomb threat that forces the plane to make an unscheduled landing in Portland. Or about the strange disappearance of Mrs. Basker, a kind, old lady who befriends the children on the airplane. Since it is her first plane trip, Gracie wonders if her imagination is teasing her; then she realizes that she and her cousins are inadvertently involved in an excit ing, frightening adventure. Lively prose and strong characterizations make an ordinary event--a first plane ride--into an extraordinary backdrop for a mystery. Roberts's clever plot enhances the suspenseful and unex pectedly humorous story. Ages 8-12. (Apr.)