Lost In Random

When in Two-Town, progress the story until you pick up a key in the Old Town Quarters. Instead of going back to the locked gate, take the first right. You will pass a creature, and will arrive to a small square with two pressure platforms on it. Stand on one, and order Dicey with to stand on the other one. Shoot the revealed target, then switch places and shoot the other target as well.
After the unlock, don't forget to cross the small bridge you just made. You will find the third page of the Storybook, along with some pots to break.