Each of you carries a Weavestone — an object pulled from you in the crossing, returned by Vell, threaded onto a cord that cannot be cut, taken, or removed by anyone but its wearer. As long as you wear it, Vell stays connected to you: he can reach you, and be reached, at any distance, whether or not the window is open. If the strand back to The Lighthouse is ever severed and Vell can't reach you, the stone pulls you home on its own — no window, no thread required, just the stone doing what it was made to do. And if the worst happens while you're wearing it, you don't simply die — you're carried to The Fold instead, where the others can still come for you. None of this works if you ever take it off.