Arnesson listened with rapt attention. I noticed that his sardonic expression gradually disappeared, and that in its place came a look of calculating sombreness. He sat for several minutes in contemplative silence, his pipe in his hand.
“That’s certainly a vital factor in the problem,” he commented at length. “It changes our constant. I can see that this thing has got to be calculated from a new angle. The Bishop, it appears, is in our midst. But why should he come to haunt Lady Mae?”
“She is reported to have screamed at almost the exact moment of Robin’s death.”
“Aha!” Arnesson sat up. “I grasp your implication. She saw the Bishop from her window on the morning of Cock Robin’s dissolution, and later he returned and perched on her door-knob as a warning for her to keep mum.”
“Something like that, perhaps. . . . Have you enough integers now to work out your formula?”
“I’d like to cast an eye on this black bishop. Where is it?”
Vance reached in his pocket, and held out the chessman. Arnesson took it eagerly. His eyes glittered for a moment. He turned the piece over in his hand, and then gave it back.
“You seem to recognize this particular bishop,” said Vance dulcetly. “You’re quite correct. It was borrowed from your chess set in the library.”
Arnesson nodded a slow affirmative.
“I believe it was.” Suddenly he turned to Markham, and an ironic leer came over his lean features. “Was that why I was to be kept in the dark? Under suspicion, am I? Shades of Pythagoras! What penalty attaches to the heinous crime of distributing chessmen among one’s neighbors?”