When Arthur discovers that Grandma Thora is a marbles champion, he trains with her so he can beat all his friends. And though Thora teaches Arthur everything he knows, she doesn't teach him everything she knows... and it's Read versus Read in the first-ever Elwood City Marbles Tournament. Brain doesn't believe in superstitions, even though his friends step over sidewalk cracks... and even Mr.Ratburn walks around ladders. So when Brain's defiance leads to a string of bad luck, he's stunned. Can he reverse the trend before the unluckiest day of them all-Friday the 13th?