A Medieval Fair has come to town, and the Aldens get grandfather's permission to volunteer their time. Benny becomes a page to the Silver Knight, a top suspect when the valuable antique sword used in the fair goes missing. But the pompous King Richard, who tends to forget that he's an actor and not a real king, seems to think the sword belongs to him. And the beautiful Princess Annabel may also have something to hide. Can the Boxcar Children find the sword and solve the mystery before the fair moves on to Silver City?