What are the signs of conscience in Tom ?

Chapter 11

Tom's conscience is short lived, but it's there;

"Then Huckleberry and Tom stood dumb and staring, and heard the stony-hearted liar reel off his serene statement, they expecting every moment that the clear sky would deliver God's lightnings upon his head, and wondering to see how long the stroke was delayed. And when he had finished and still stood alive and whole, their wavering impulse to break their oath and save the poor betrayed prisoner's life faded and vanished away, for plainly this miscreant had sold himself to Satan and it would be fatal to meddle with the property of such a power as that."

Later, in the same chpater;

"Tom's fearful secret and gnawing conscience disturbed his sleep for as much as a week after this....."

While on the Island, Tom constantly wrestled with his conscience for running away and stealing food from others. Tom felt so guilty that he couldn’t sleep, “then conscience granted a truce, and these curiously inconsistent pirates fell peacefully asleep." Page 498

Tom tries to ease his conscience by smuggling “small comforts” to Muff Potter in prison. In the end Tom tells the truth and saves Muff Potter.