Tommy Williams was a young inmate at Shawshank State Penitentiary. He arrived in 1965 on a two year term for breaking and entering after he was caught stealing TV sets from JC Penney. He had a wife and a young daughter.
Andy Dufresne had been helping other inmates to get their GED, and Tommy wanted to get his. Andy said he didn't waste time on losers, and after being convinced that Tommy was committed, he took him under his wing, teaching him how to read. By 1966, Tommy was ready to take the test. Tommy gets frustrated and gives up on the test, but Andy sends it in anyway. Tommy later finds out that he passed with a C-plus average.
Later, Tommy feels like he has let Andy down. Red tells him that Andy is proud of him, and they start talking about Andy. When Red tells him that Andy was a banker on the outside and that he caught his wife with a golf pro, Tommy is stunned.
Tommy later tells Andy and Red that while he was in Thomaston for carjacking, he shared a cell with Elmo Blatch. There is a flashback and Blatch is telling Tommy that he killed a golf pro and his "tasty bitch" while robbing them. He says that they pinned the crime on some "hotshot banker", meaning Andy.
Andy later tells the warden about this, but because the warden is corrupt and does not want Andy to tell anyone about his money laundering operation, he dismisses it. Andy insults him and is sent to The Hole for a month.
The warden calls Tommy in the middle of the night to talk to him outside. The warden asks him whether or not what he said to Andy and Red was the truth. When he answers affirmatively, the warden gives a signal to Captain Hadley to shoot Tommy from a tower. Four shots ring out and Tommy falls to the ground, dead.
The warden later visits Andy in solitary and tells him that Tommy tried to escape and that it broke Captain Hadley's heart to have to shoot him. Andy sees through this, and tells him that he is done working the books for the warden. The warden flies into a rage and tells him that if he stops working for him he will make his life as miserable as possible.
After Andy escapes from Shawshank, Red surmises that after Tommy was killed, Andy had figured he had been there long enough.