Swelter’s feet began to move the treadles of the grindstone, and it began to spin in its circles. He spat upon it rapidly three or four times in succession, and with a quick movement slid the already razor-keen edge of the cleaver across the whirr of the stone. Doubling himself over the grindstone he peered at the shivering edge of the blade, and every now and then lifted it to his ear as though to listen for a thin and singing note to take flight from the unspeakable sharpness of the steel.

Then again he bent to his task and continued whetting the blade for several minutes before listening once more to the invisible edge. Flay began to lose contact with the reality of what he saw and his brain to drift into a dream, when he found that the chef was drawing himself upwards and travelling to that part of the wall where the chalk lines ended and where the arrow pointed to the Ninth staircase. Then he removed his shoes, and lifted his face for the first time so that Mr Flay could see the expression that seeped from it. His eyes were metallic and murderous, but the mouth hung open in a wide, fatuous smile.

Then followed what appeared to Flay an extraordinary dance, a grotesque ritual of the legs, and it was some time before he realized, as the cook advanced by slow, elaborate steps between the chalk lines, that he was practising tip-toeing with absolute silence. ‘What’s he practising that for?’ thought Flay, watching the intense and painful concentration with which Swelter moved forward step by step, the cleaver shining in his right hand. Flay glanced again at the chalk arrow. ‘He’s come from the ninth staircase: he’s turned left down the worn passage. There’s no rooms right or left in the worn passage. I ought to know. He’s approaching the Room.’ In the darkness Flay turned as white as death.

The two boxes could represent only one thing – the door-posts of Lord Sepulchrave’s bedroom. And the sack …