In Jensen County, David is sentenced to 60 days in a work camp known as "The Slam" for destruction of private property (fence already broken down) trespassing (no sign about it), stealing an apple (from an overhanging branch!), and no representation in court. Protests at the unfairness of this all the way to The Slam are to no avail. The only charge David concedes may be valid is vagrancy.
The warden, Captain Holt gives David very stern warnings about what happens if he makes trouble, and the camp runs to a rigid system of army-inspired discipline and organisation that must be adhered to. The prison staff address prisoner by their numbers. Holt has an odd pathological worship of Napoleon as an icon of discipline and being persecuted for it, but returned to triumph (no mention of Waterloo). David soon learns they use hot boxes as a punishment, but one man, John Blake, won't be broken by it.
David is soon accepted after helping nurse Blake after his hot box ordeal. David learns from another prisoner, Doc Alden, that the county makes big business out of bringing able-bodied men to the Slam on "a petty bum rap" like his. Men brought to the Slam on such raps are rented out to farmers and companies to do their dirty labour.
Blake plots an escape, and David arouses suspicion when he overhears. Some men talk of killing him. In the end they settle on taking David with them.
Next day David is on the roadside chain gang with the others. One Mr Rader pulls up and gives the guard Holt's cut for the labour. Blake is still determined to escape, despite David's warnings that he is not up to it after his hot box ordeal. Blake goes ahead, with David chained to him, and two other prisoners do likewise. But Holt soon catches up and Blake realises someone informed on them. He takes Holt hostage, but the other two prisoners refuse to run. So Blake and David do so once the guards put down their guns, but the chase is soon on again.
When David and Blake cross a wooden plank bridge it snaps and they fall into a dry creek. Blake is knocked out while a rattlesnake bites David, which triggers a hulkout. Hulkouts bring on accelerated healing powers, which make short work of the snake venom. The Hulk soon deals with the rattlesnake. The hulkout also breaks the chain binding David and Blake together. The Hulk carries Blake away and lays him down for Holt to find. When Holt does, the Hulk attacks him and upends his vehicle, and carries Blake off again.
But the Hulk has to change back into David eventually, and so David and Blake are recaptured. They are put in the hot boxes, and Blake gives David tips on how to survive it. Doc smuggles them some water later and delivers some news: one of the guards was so shaken after the Hulk attack that he has talked to the press about Holt. Reporters will arrive tomorrow at noon. David suggests a petition full of grievances and slipping it to the press.
When David and Blake are released from the boxes, Holt warns them not to make trouble when the visitors come. But when the press arrive, David is dismayed to see McGee in the crowd, asking questions about the Hulk that the guard reported. Holt tells him the guard was fired for drinking on duty. However, David can't deliver the petition as instructed or McGee will recognise him. Holt intercepts the petition and Blake is thrown back into the hot box because of David's failure. The press leave, but McGee suspects they were not shown everything.
After this, the prisoners turn against David and call him "a fink". Holt tries to recruit David as a privileged prisoner and even reduce his sentence in return for keeping him informed. David declines, but Holt is confident he can change David's mind.
Meanwhile, the prisoners get violent towards David. On the next work party they damage David's leg with a spade and the guard asks him if he will change his mind now. David still refuses and is put aside in the truck. He sees the guard paying off one of the other prisoners, Harris, and realises Harris is the informer.
Back in the barracks Doc tends to David's leg. David tries to tell Doc about Harris, but Doc does not believe him. In an effort to convince the others, David tries to talk to Harris about an escape in front of them, and eventually succeeds in planting a seed of doubt in Doc's mind. Doc decides to watch the gate that night as David suggests, and soon discovers David was right.
Meanwhile the prisoners throw a blanket over the sleeping David and beat him up through it. But they are very surprised when huge green arms emerge from the blanket, seize them, and throw them against the wall. Of course they had triggered a hulkout, which also heals the leg.
Doc bursts in with his news about Harris, and is very surprised to see the Hulk, who then starts smashing up the barracks, the guard towers and the hot boxes. The prisoners look on, stunned, and the guards are staggered.
The Hulk disappears for a moment and the prisoners go into open revolt against the guards. When Holt threatens to open fire on the prisoners, the Hulk stops them and then rips open the gates. Blake takes Holt prisoner and says he will stay and testify or Holt will continue his dirty work, while another inmate decides to just make a run for it. Doc informs Blake that Harris was the informer, not David. They ponder where David is and Doc jokes that maybe David made his break (forgetting David had an injured leg and not knowing the hulkout would have healed it). Blake calls the state police.
In another county a man picks up David. In his pickup there is a newspaper, which informs David that the Slam officials have been indicted and the prisoners are getting reduced sentences. There is a photograph of a triumphant Blake and Doc talking to the press. The driver says it sucks and is glad they have nothing like it in their own county. But they pass by another roadside chain gang as they drive along, and David is disturbed at the sight.