Answer & Explanation:
Jem, Dill, and Scout decide to take a walk in chapter 6 along the way that when the four reason are found to why they peek into the Radley window.
Two of the reasons have to do with the darkness.
1) no one will see them in the darkness
2) Atticus would be so immersed in a book such that he wouldn't hear them or notice they are gone.
3) If they get killed by Boo they will only miss school instead of vacation.
4)The dark house is easy to see in the dark that during the day
The line is: "We thought it was better to go under the high wire fence at the rear of the Radley lot, we stood less chance of being seen. The fence enclosed a large garden and a narrow wooden outhouse."
I agree with Jem who wants to go back and try to retrieve the pants cause if he could succeed that would eliminate the evidence that would be used against him.