Episode 39 of The Witness opens at a pale pink panel above a glass floor, where any line drawn on the panel also lights paths on the floor. Basket works out two routes through it, solves blue panels half hidden behind wooden posts, and ends in a white room where the panels flash through colors. The video stops right after one of those flashing panels is solved, with the next one lit.
Paths on the floor
The video picks up mid-thought at the pink panel: "you have to draw a shape around this." Every line drawn on it shows up as a wide path on the floor. The first full solve turns those paths purple, and they run down into a room below.
Back at the panel, the commentary notices that "you can actually walk through here" in one spot but not in another, and the goal becomes a route through "that middle section." After many tries, "This might do it." A second solve leads into a wooden room hung with pencil sketches of buildings, which "seems to actually be for that treehouse."
Posts in the way
Next comes a dark room of blue panels behind posts and beams. On the first, "there's a thing in the way," with a white dot hidden behind it, and "there's also a mirror": two lines are drawn at once. "I can't draw over this thing but my reflection can," so the drawing starts from the other side, and it works: "that has turned on this puzzle that we cannot see very well." That one falls after a change of angle: "I think we can solve it from here. Yes, good."
The last sits behind two crossed beams, "a mirrored puzzle" where "we have to cross all the dots." As the commentary sums it up, "I can't draw on the puzzle when I can't see it," so each answer meant finding "a different angle." The cables beside it light blue, and "that door is open now."
The shortcut
Back at the pink panel, the job is now "going to the other side." The line runs "through this little shortcut, yes, good," and the new path leads outside to a view over the island. The commentary points out "the Tetris stuff," "the windmill," and "a puzzle we could never solve," then goes downstairs into a white room with flowers spilling down one wall.
Flashing panels
A row of square panels sits beside black screens. The yellow one and an orange and teal one go quickly. The next, magenta and green, keeps flashing through other colors, and its dots "seem like they're blinking at different rates." The commentary groups dots that blink alike, and route after route goes in and comes back out. One guess fails because "this one is actually yellow in this universe."
Where it ends
After about four minutes, a line from the bottom left goes in and the purple panel to its right lights up. The commentary is still talking it through when the picture fades to the end card.