Mandie and the Buried Stranger

It's spring break from the Misses Heathwood's School for Girls, and Mandie can't wait to get home and see her friend Joe Woodard. When he left on the train to go to college after the Christmas holidays, he yelled something out the train window that she couldn't hear, and she's been anxious to find out what it was ever since. But when Mandie and Joe get together, she becomes shy around him and doesn't understand why. Then while they are one their way to see Sallie Sweetwater, they discover a huge pile of mica and no one knows who moved it there. It's an even bigger mystery when the whole mound totally disappears the next day. Who would do such a thing, and why? And who has been stealing wagons? Are the two related? Will Mandie ever find out what Joe said from the train?