The boy had imprisoned the stone in a twine net: two sets of helices, one climbing clockwise, the other anti-clockwise, intersecting each other in a pattern of diamonds, just like the lead net that held Clarke's window together. Enoch didn't suppose that this was a coincidence. The work was irregular at the start, but by the time he'd completed the first row of knots the boy had learned to take into account the length of twine spent in making the knots themselves, and by the time he reached the end, it was as regular as the precession of the zodiac.