Garth rings from another one of his books before introducing tonight's episode as a 'what if' along the lines of Planet of the Apes. He dedicates tonight's episode to his wife Pam. The Channel 4 logo comes on, Garth falling through space and then the usual main opening sequence.
Zooms into Darkplace, Rick enters the staffroom and tells Sanchez to get up. He goes for a drink of water and fails but doesn't seem to mind that it is bright green. When Rick comes back in he finds Sanchez looking like an ape. The episode name and number are announced looking onto Darkplace though it seems to be submerged in the green water.
Cuts to Garth in an interview followed by Dean. Rick and Sanchez are in the car; Rick introduces himself and says that other people seemed to be turning into apes. On he way to Thornton's office Rick goes to see the kid and says he bought the drugs the kid needed out of his own pocket. Cuts to Dean in an interview saying that he punched the kid for insulting the script.
Rick is about to take a drink of water but is stopped when Thornton calls him in. Sanchez gives Liz some water; Thornton and Rick have a coffee. They all drink and soon Liz is an ape too. Sanchez is called away to surgery, Thornton tells Rick to get on the ape problem and Rick and Liz go to see the padre.
Todd talks about the makeup used for the apes and says that it still looks great. Rick arrives to see the padre and asks for some water but the padre says the water is his. He refuses to give him any information and was a weird smile when Rick leaves, he is turning into an ape.
There is an emergency in surgery and Sanchez comes out complaining about his ape hands. Cuts to Todd talking about getting into character as does Dean. Rick talks to Sanchez but Sanchez knocks him out and Rick has a strange dream. When he wakes up he sees Liz in front of him.
Rick realises he has been a sleep for a month and the apes now rule Darkplace. He looks out and sees the apes dressed like guerrilla fighters. Thornton decides to have some water and says the hospital is running really well. He says they will be able to build the kiddie wing but Rick says they can't do it this way. Rick remembers all the instances of water and realises that it is the water.
Rick tells Thornton to stop and he does. He is ok because he only had a tiny sip. Rick heads off to the water store room. Cuts to Dean talking about why Thornton didn't turn into an ape. Then to Garth talking about using subtext. Rick shoots two of the apes and heads into the store room. He finds the padre urinating into a water bottle held by Sanchez. Rick is discovered and Sanchez attacks him, forcing him to fire 3 shots into the air. Rick then shoots out the boxes and they fall on Sanchez from above.
The padre now totally ape runs off and jumps on a bike. Rick follows him on another bike and a chase through the wood begins. There are engine sounds despite them being on push bikes. Thornton joins the chase on another bike and tries to get him to pull over but the padre knocks him off the bike. The chase then continues on foot and Rick chases the padre over an assault course. He finally catches him and they smash into a pile of boxes, Rick punches him.
Rick says he is sweating and it goes to Garth talking about why you shouldn't use anti persprint. Later they talk about what happened and Rick quickly explains while the camera looks away and Rick explains that he developed an antidote which is why everyone is back to normal.
Later Rick gives a voice over from the roof looking out over the crimson sky. Fades to interviews with Dean and Garth talking about Liz and how she is missing presumed dead. Original screen footage of Liz is shown while the credits roll. Ends with Dean saying he thinks Liz is buried in the Eastern block.