The girls didn't see them.
Yes, they did. This is from the end of Chapter Nine:
After a little exercise in mental trigonometry, Karen concluded that the tree was truly gigantic -- at least seventy, perhaps as much as one hundred feet high. The trunk, at the base, was at least two feet in diameter. And the top two-thirds of the tree was definitely visible through the hole in the roof. If they could set it ablaze, it would illuminate the whole hillside, and would burn for a long time. They had their signal.
But, Emma reported, the clouds were moving in, and it looked like rain. They needed to get started.
Or, if you mean that the girls didn't see Superman and Walter --
Their upward progress abated, and Walter looked around. "How high up are we?"
"At least fifty thousand feet; this is higher than the highest commercial jets fly. You can still breathe because of the 'aura.' No one on the ground could possibly see us, even in the daytime, unless they had telescopic vision and happened to be looking right at us.
Its good idea. :rolleyes: If start raining at least the smoke will signal.
Is also dangerous with the car probably losing gasoline.
Time is running