How do Bill and Sam finally get rid of Red Chief?

Red Chief's real name is Johnny Dorset. Bill and Sam kidnapped the young boy from Ebenezer Dorset because they believed that the man would pay the big ransom demand to get his son back. Unfortunately for Bill and Sam, Johnny Dorset is more than a handful. The boy turns the tables on his captors, and Bill and Sam look for just about any opportunity to get rid of the kid.
The two kidnappers write the ransom letter to Mr. Dorset, but instead of paying the ransom, Mr. Dorset offers the kidnappers an alternative proposal. He wants Bill and Sam to pay him $250 dollars to take his own son back. Bill and Sam think that is a great deal. 

"We’ll take him home, pay the ransom and make our get-away."

The two men return Johnny Dorset at midnight, pay Ebenezer the money, and run as fast as they can out of town.

It was just twelve o’clock when we knocked at Ebenezer’s front door. Just at the moment when I should have been abstracting the fifteen hundred dollars from the box under the tree, according to the original proposition, Bill was counting out two hundred and fifty dollars into Dorset’s hand.