In To Kill a Mockingbird, Dill dares Jem to run the Radley house and touch the wall. When Jem does this, what do the children notice?

Jem, Scout, and Dill were fascinated with the rumors they had heard about Boo Radley.  They were determined to catch of a glimpse of this mysterious figure.  Dill dared Jem to go up and touch the side of the Radley's house.  This was an unusual request, because the Radley family kept to themselves.  They did not welcome visitors, as other local families did.  They preferred to stay inside with the windows shut and the shutters...

Jem, Scout, and Dill were fascinated with the rumors they had heard about Boo Radley.  They were determined to catch of a glimpse of this mysterious figure.  Dill dared Jem to go up and touch the side of the Radley's house.  This was an unusual request, because the Radley family kept to themselves.  They did not welcome visitors, as other local families did.  They preferred to stay inside with the windows shut and the shutters closed.  They did not leave their front door open on Sundays, and they did not even have a screen door.

With hesitation, Jem approached the Radley house.  He looked around carefully before running through the gate and touching the house.  He ran out of the yard quickly.  The three children ran back to the Finch house and stopped at the porch.  They stared back at the Radley house and they noticed something:

The old house was the same, droopy and sick, but as we stared down the street we thought we saw an inside shutter move.  Flick.  A tiny, almost invisible movement, and the house was still (To Kill a Mockingbird, Chapter 1).