Episode 42 of The Witness opens at one more of the flashing color panels and solves it in under a minute. Basket then looks through a room of sketches of the island, works a panel over a glass floor, and arrives at a row of panels where a single line is drawn on all of them at once. Most of the video goes to two of those combined puzzles. It ends right after the second one is solved, with the next panel lit.
One more flashing panel
The panel at the start keeps cycling through colors, but the commentary sees that "all the dots are really actually staying the same color, even though the background is moving." That makes it quick. The line goes in, the pink cable beside it lights up, and the reaction is "see that one is so easy. Why wasn't this one so easy?"
Sketches of the island
Down the stairs is a room with drawings pinned to every wall. The commentary picks out "the water that I drew on," "the windmill there," and maybe "the starting area," and decides these are "probably just concept art" rather than hints.
A panel over the glass floor
Past some plants, a gray panel with sun symbols hangs above a glass floor, and the line drawn on it also shows up on the floor below. "We need to have the suns grouped together." A solve lights wide paths across the floor, but a try at walking over to them ends with "Seems like I can't."
Composite puzzles
Next is a wall of small panels beside black screens. The first few are simple: cross a dot, separate two things, group things together. Then one line starts appearing on every panel at once. "Oh man, okay, so it's like composite puzzles." Three panels go together quickly. Four take about eleven minutes. Every route breaks a rule on some panel: the white and black dots end up together, or "the green sun is separate from the other sun." The way through comes from a shape: "It has to be inside the same blob," not in the exact spot it seems to point to. At about 16:30 all four light green.
Five at once
The fifth panel adds an extra black dot and a pink sun, and the commentary notes the last panel in the row "is burnt out." Routes get drawn and dropped for six more minutes, and at one point the commentary groans, "I clicked a button. I hate when I do that."
Where it ends
The final line goes in with "Alright, will this work?" All five panels turn green and the sixth panel to their right lights up. "The suns are happy and these other ones are good," the commentary says, and the picture fades to the end card.