Back at Grandfather's place, they don't know if Arthur actually got the keys or not. But they do know it's time to vacate, since the water levels are rising.
So they set out, and wade through a bunch of water… only to end up in one of Snatcher's traps.
This time, though, Snatcher's minions aren't fooled, and they identify William (Grandfather). Everyone gets stuck in sacks and brought up to the Cheese Hall.