Isaac blinked and heaved a sigh. He seemed inordinately relieved. Perhaps he had feared that Daniel would dispute what he had just said: You had the calculus from me first-hand . That was the key. In Daniel, Isaac saw a witness who could testify to Isaac’s priority in the discovery of the calculus. Whatever other annoying and inconvenient qualities Daniel might have, vanished when placed beside that. Daniel felt the muscles of his scalp and neck easing, felt his lungs filling with air. He was going to be all right. He’d make it out of the room whole, even if he said things that made Isaac a little angry. To Isaac, Daniel was more than a pawn; he was a rook, kept sequestered in the corner of the board until the end-game, then brought out at last to sweep inexorably down the board, driving the foe back to the last rank and forcing surrender. Isaac would put up with a lot, from a rook.