- Travers used to be a correctional officer at Alcatraz. His superior was a man named Ned Leech. One evening, Travers found Leech running along the corridor through the pen, chased by Wai-Chun and several of his gang. Leech threw his keys to Travers to keep them out of Wai-Chun's hands. A prisoner named Reinkemeyer grabbed Leech and pressed a stolen carving knife against Leech's neck. Travers killed Reinkenmeyer with his rifle. The other men fled, straight into the arms of guards with nightsticks. Leech punched Wai-Chun then kicked him when he was down.
- That night, the prisoners were agitated. As Travers patrolled the cell block, one of the inmates, Richard A Fells, asked him what it felt like to kill a man. Travers didn't answer, and Fells went back to his book.
Travers tells the young man that Fells, who had a weird Irish or Scotch accent, gave him the creeps. He tells the man that the only person enjoying himself during that time was Leech. And the man Fells seemed to be waiting for something to happen.
- A week or two later, the prisoners were in the canteen, eating spaghetti. Travers noted that Fells was talking with Wai-Chun, almost provoking him to anger. It finally worked, and the place erupted into fights. Several officers fell, but Travers couldn't get there in time. Leech, in the middle of the fight, ordered one of the officers to release the lethal poison gas. Men started screaming then went silent.
- Suddenly Travers noticed that he was still alive. The gas stopped in mid-air inches from his face. He noticed that Fells was with him, and Wai-Chun as well, holding the limp and beaten body of Leech.
- Fells triumphantly confronted Wai-Chun, explaining to Travers that Wai-Chun was a Threckon that he had imprisoned some time back. Free, it came to Alcatraz and took over Wai-Chun's body, looking for anger to feast upon. Fells, learning that the Threckon had escaped, smuggled himself into Alcatraz to find him. The Threckon created a telekinetic bubble to save himself from the gas.
- Wai-Chun acted as if he didn't know what Fells is talking about. Travers noticed that Leech had recovered from the beating and stood up, but blubbery flesh started coming out of him, turning into tentacles. Wai-Chun threw himself out of the way in terror, but crossed the invisible barrier and died from the gas. The Threckon attacked Fells, seeing the Time Lord as a feast of anger. Travers shoved “Leech” outside the barrier, then collapsed as the barrier collapsed and he began breathing the toxic gas.
Travers tells the young man that Fells saved him, but he never saw him again. Travers became a cop, but is now suffering from lung cancer, caused by breathing the gas.
- The stories in Short Trips: Steel Skies are divided into four sections dealing with different types of confinement. This story deals with incarceration, that is, "punishment and imprisonment".
- The Eighth Doctor makes a cameo at the beginning and end of this story.
to be added