Harrison Beck is reluctantly joining his travel-writer Uncle Nat for the last journey of the royal train, The Highland Falcon. But as the train makes its way to Scotland, a priceless brooch goes missing, and things are suddenly a lot more interesting. As suspicions and accusations run high among the passengers, Harrison begins to investigate and uncovers a few surprises along the way. Can he solve the mystery of the jewel thief and catch the culprit before they reach the end of the line?