Sleeping Dirty begins with a man hanging from his feet, being whipped repeatedly. He's a large, muscular man with long hair and a patch over his right eye. The whipping stops as a short, fat man with a moustache emerges from the shadows. He asks the man if he'll cooperate and also reveals that the man's name is Kiel Aronnax. Kiel asks the short, fat man if the ARMS is here. The short man doesn't give him an answer. Instead he has a door open up below Kiel. It reveals a long hole with spikes sticking out of the ground, along with many dead bodies. When asked if he'll cooperate again, Kiel still declines. The fat man has the rope cut and Kiel begins to fall. Fortunately the trapdoor quickly closes before Kiel falls through. The short man begins laughing at Aronnax just as a guard enters and tell their Boss that there are trespassers on the grounds.
The scene quickly changes to two women and a small furry animal who can talk. They're sitting down eating and reading magazines. One of them reads article from their magazine, out load; "Alcatraz Penitentiary proudly announces that since it has opened there have been no escapees. Rumor is the Government is hiding something top secret hidden in its underground safe." Soon after, the girls are discovered as lights are flashed on to the crate they're riding down in to the Prison. One of the girls throws two cards as they explode and destroy the search lights on them.
The scene changes back to the Prison room with the short man, who we believe to be the Alcatraz Boss. A guard shouts to him that Aronnax has escaped during the intruder interruption. We follow Kiel has he dodges past the security, running down hallway after hallway. He leans around a corner just as a gun is pointed at his back. He turns around to find two women and a small rat looking up at him. He recognizes them as the trespassers. They tell Kiel to take them to the safe.
Kiel and his new-found friends jump down from an air-duct and see a giant container ahead of them. It's the safe. Kiel, who happens to be a Doctor and is quite familiar with the Prison's computers, manages to break the codes and open the safe. The door opens and the three of them look through the mist to see a little child. He's asleep, on his back, and floating in mid-air. The guards realize they've broken in to the safe and head towards it. Kiel tries to wake the boy up. He raises his hand to hit the boy, but he wakes him up and a huge explosion rips through the safe. The smoke clears to reveal that the entire safe has been blown apart. One of the female thieves, who was knocked over by the explosion, gets up and sees a strange object wrapped in cloth. The young boy also wakes up and frantically begins searching for his "buddy". He sees it in the hands of the other thief, who is holding a small gun. He tells her that it belongs to a real man. He sees the older, attractive thief and asks her name. She replies with Loretta Oratorio. Dr. Aronnax asks the young boy his name and he replies with Cheyenne Rainstorm, just as the doors are blown open and the guards emerge. They open fire on the crew as they duck behind a large piece of metal. Dr. Aronnax takes the guy from the thief's hand and begins to fire at the guards, but nothing happens. He realizes it's the ARMS. The young boy tells him to give the gun to him. It's at this point Cheyenne realizes he isn't the 25 year old man he says he is; He's become a boy.
The thieves' animal friend notices that Cheyenne has a serial number inked to the bottom of his right foot. He has a flashback of himself being shot and falling to the ground, but he cannot remember anything after that. Loretta points to an air duct on the far wall but it's bolted shut. She is going to blind the enemy using her cards while Cheyenne shots the bolts out of the air ducts cover. The cards fly out, and as expected, all the guards look up at them. They explode into a bright a light just as Cheyenne finishes off the bolts. Aronnax, Cheyenne and the thieves make a run for their new exit.
They make it down the air duct as it drops downward. Soon, a bright light approaches as they realize what's below it; Nothing. The Prison is a giant floating island. It is exposed by magnetic rocks that slowly rotate it around an enormous canyon. Dr. Aronnax manages to get a hold of the ledge with everyone clinging on to him. Cheyenne learns that the Prison only makes a stop once a year, when it revolves around the canyon back to the station. A rope falls down them from Mirabelle, who somehow used Magic to get back on to the flat ground.
When they reach the end of the rope, Mirabelle is being held by Mr. Kihano, the Boss of Alcatraz Penitentiary. It was a trap. He is caged in along with Mirabelle as he calls in the Alcatraz Executioner, known as The Falconvein. A giant monster emerges from a door at the top of a flight of stairs. It's a large creature with a long neck and two sharp, curved arms and visor-like eyes. Aronnax, Cheyenne and Loretta begin to run as the creatures back starts to spark. The Falconvein shoots a large, yellow energy beam out of its mouth. Loretta uses one of her cards to reflect the beam. Loretta then remembers the large, wrapped object she found in the Safe. She shows it to Cheyenne, who recognizes it as Batour. The Falconvein corners Loretta and Dr. Aronnax.
Cheyenne locks the smaller ARMS gun in to the side of Batour, making a hand-held cannon. He aims it at The Falconvein and fires. A large, purple beam shoots forward. The creature turns and fires a beam from its mouth. The blast from the ARMS is too powerful and hits the creature, tearing it apart. Mirabelle quickly turns in to a small bat and flies out the cage with Mr. Kihano in it. Mr. Kihano runs after her but falls over after nearly running off a ledge.
Cheyenne approaches the now helpless Prison Boss and asks him where his body is. Mr. Kihano tells him he doesn't know. He was responsible for guarding Cheyenne's brain and fake body. Cheyenne points the gun at Mr. Kihano's back and says "Bang". Mr. Kihano stumbles forward and falls in to the canyon below. The crew realizes they have no way off the Prison Island. Not for another year, at least. Cheyenne kicks back and takes a nap; he knows they'll be here for a while.