What is inadvertently prevented from happening that night at the jail by Scout in Chapter 15 of To Kill a Mockingbird?

After a group of Atticus' friends had congregated on the
front lawn one Saturday just before the trial of Tom Robinson began, Jem and Scout began
to worry about the safety of their father. The next evening, when Atticus left the house
"carrying a long extension cord" with a light bulb attached, they wondered where he was
going. When he decided to drive the Chevrolet--Atticus always walked to his office--they
knew something was up. So, after pretending to go to bed, Jem and Scout rounded up Dill,
and they sneaked down to the town square. They eventually found Atticus sitting in front
of the jail, reading under the light of the extension cord he had taken with him. Before
they could reach him, a group of cars arrived, and the men inside confronted Atticus.
The children rushed to him, sensing something was not right. Scout had no idea what was
happening, but after kicking one man in the groin, she began making innocent
conversation with Walter Cunningham Jr.'s father. The men suddenly decided to leave, and
it was only the next day that the children realized that the men had come to the jail to
remove Tom Robinson--and lynch him.