Gigi, Knox, and Brady examine the contents of Knox’s puzzle box: cotton balls, nail polish remover, yarn, wrapping paper, and sunglasses. Knox connects the cotton balls to nail polish remover, while Brady suggests the liquid may only resemble nail polish remover chemically. Gigi considers invisible ink but notices there are two cotton balls and two lenses, which leads her to test the liquid on the sunglasses.

When Gigi rubs the lenses with the liquid, a dark coating comes off and the lenses turn red. Knox flips over the wrapping paper, revealing a red back. Gigi puts on the altered sunglasses and sees three hidden symbols on the paper, then the group locates the same symbols among the carved markings on the bookshelves.

Gigi proposes pressing the three matching symbols at the same time. Although Knox notes the symbols did not move before, Gigi argues they had not tried simultaneous pressure. Gigi presses two symbols while Brady presses the third, and a hidden door opens in one of the bookshelves.

The three enter a small room with a tile floor and corkboard walls filled with colored pushpins. Gigi realizes the yarn must connect the pins, and Brady identifies the colors as rainbow-based. Gigi uses the Roy G. Biv order, and the stretched yarn creates shadows across the tile floor that point to a single central tile.

Knox pushes the marked tile, opening another trapdoor and staircase that lead out behind the house onto the rocky shore. Dawn is close but the sun has not yet appeared, so the team still has a narrow chance to reach the dock in time. Knox and Brady sprint ahead, and Gigi forces herself to keep pace across the rocks until her toe catches and she falls.