She heard Mr. Ganz inhale sharply. After a second he said, “King to bishop one.”

“That’s mate in three,” Beth said, without turning. “First check is with the knight. The king has the two dark squares, and the bishop checks it. Then the knight mates.”

Mr. Ganz let out his breath slowly. “Jesus Christ!” he said.

They were watching the Saturday-afternoon movie when Mr. Fergussen came to take her to Mrs. Deardorff’s office. It was a movie about table manners called “How to Act at Dinnertime,” so she didn’t mind leaving. But she was frightened. Had they found out that she never went to chapel? That she saved pills? Her legs trembled and her knees felt funny as Mr. Fergussen, wearing his white pants and white T-shirt, walked her down the long hallway, down the green linoleum with black cracks in it. Her thick brown shoes squeaked on the linoleum, and she squinted her eyes under the...