The Secret Santa

It's a Ho! Ho! Ho-rrible trick!
Christmas is coming, and Nancy's third grade class is having a Secret Santa exchange. That means cards, candy, and a special gift for everyone. Everyone except Nancy Drew!
Is it a mistake? Is somebody just being silly or mean? Or is someone hiding something and afraid to tell the truth? One thing's for sure. Nancy's presents are gone, and all she has to unwrap is one big mystery!