Dreamcatcher is set near the fictional town of Derry, Maine. It is the story of four lifelong friends: Gary Ambrose "Jonesy" Jones, Pete Moore, Joe "Beaver" Clarendon and Henry Devlin, who save Douglas "Duddits" Cavell, a young teen with Down syndrome, from a group of sadistic bullies. The four friends grow up and away from Duddits, but maintain close bonds with each other, sharing memories of Duddits and their good times together. Each has his own troubles: Beaver is terrible in relationships, Pete is an alcoholic, Henry is suicidal (unknown to his friends), and Jonesy almost died from a severe car accident from when he walked into open traffic, having seen a vision of Duddits calling to him.
The four go on a hunting trip together each year, and plan to visit Duddits on their return from this year's trip to the Hole-in-the-Wall (a cabin in the woods). While on the trip, Jonesy finds a disoriented and delirious stranger wandering in the woods during a blizzard, and talking about lights in the sky. The man exhibits dyspepsia and extremely foul flatulence but claims that these are the result of eating berries and lichen while he was lost; he has a reddish discoloration on his face, which he dismisses as an allergic rash. Beaver and Jonesy notice large numbers of animals, all with a similar reddish discoloration, migrating.
Henry and Pete, driving back to the cabin, lose control of the car and crash when avoiding a woman sitting in the road. Pete's leg is injured, but Henry is unscathed. They approach the woman, who mumbles about lights, mentions the man found by Jonesy, and displays the same foul flatulence and burps. Henry and Pete drag her to a safe clearing; Henry goes to find help and tells Pete to stay with the woman and not to go back to the car for the beer.
Beaver attracts the attention of rescuers in helicopters, and is told that the entire area has been put under quarantine. The army quarantine is headed by Colonel Abraham Kurtz.
On returning to the cabin, Beaver and Jonesey find the man dead on the toilet, and the floor covered with his blood. They hear the toilet water splashing; Beaver sits on the toilet lid, trapping something inside it. Jonesy rushes to the garage to find duct tape to seal off the toilet while Beaver holds the lid down with his body weight; the creature trapped inside keeps trying to escape. Beaver has a nervous habit of chewing on toothpicks; as he tries to take one from his pocket, the creature hits the seat, and Beaver spills all the toothpicks on the blood-covered floor. One toothpick lands on a clean tile, and Beaver bends down to retrieve it. The trapped creature hits the lid from inside the toilet; Beaver loses his balance and falls to the floor, freeing the creature, which then attacks him.
The lost man, his hunting companion the woman, and the stampeding animals all have similar symptoms caused by infection with an extraterrestial macro virus. Army scientists named this The Ripley, after the protagonist of the Alien series, partly because of its extreme resilience to destruction. The friends discover that eating or inhaling the red mold causes large worm-like aliens, called byrum (derived from the name of the alien mold, byrus) to infest the host. Byrum are red, lamprey-like creatures with multiple rows of razor-sharp teeth; a second form of byrus grows on open wounds and mucus membranes. When an infestation is sufficiently established, the host develops a form of telepathy with other infested individuals. The friends name the byrum "shit weasel" because it exits the body through the anus, killing the host.
Byrum are highly aggressive and, although small are more than capable of killing a human. The byrum matures into a form called a Grey; in their normal environment they would maintain a symbioticrelationship with their host, but the cold environment causes them to react badly and kill their earthly hosts. Once outside the host they die quickly in the cold, as does the byrus fungus.
Colonel Kurtz states that the Greys have tried several times over the past century to attack and gain control of earth, but have failed. This time the Greys are outside a crashed spacecraft, sending radiomessages stating that they come in peace and are helpless, to try to fool the Army. Several helicopters are sent to wipe out the Greys; they mainly succeed, but many of the soldiers are exposed to the byrus in the attack. Meanwhile, all people in the area who have been affected by the byrus fungus are rounded up by the Army, with the intention that they will later be executed.
Jonesy returns to the bathroom, to discover Beaver being killed by the byrum. Beaver uses the last of his strength to hold onto the byrum to prevent it attacking Jonesy, who closes and bolts the door. The byrum begins to break through the door, and one of the escaped Greys appears behind Jonesy, takes over his body and controls it – with difficulty as the human body is so different to its own. Back in Derry, their childhood friend, Duddits, cries and screams to his mother, "Beaver's Dead! Beaver's dead!"
Pete, who had returned to the car for the beer, makes his way back to the woman but finds her dead; the shit weasel has made its escape from her body and attacks Pete, who defeats it by throwing it into a fire they had built for warmth. His battle with the byrum exposes him to the byrus fungus, which begins to cover his body. Henry, meanwhile, gets to Hole-in-the-Wall, and discovers Jonesy taken over by the alien, Mr. Grey. Mr. Grey uses Jonesy's body to leave on a snowmobile. Inside the house, Henry finds Beaver's dead body and the shit weasel that killed him in the bedroom. The byrum is weak from the cold; Henry shoots it and burns a clutch of eggs which it had laid. Henry leaves to seek help, but is captured by the army and placed in quarantine.
Flashbacks to their childhood reveal that each man gained a certain degree of telepathy from being in contact with Duddits, who has special powers. Through their friendship and Duddits' powers they find a missing girl, trapped from falling down a hole.
Jonesy battles Mr. Grey in his mind, stealing and locking away his memories of Derry and Duddits from Mr. Grey. While Mr. Grey is in control, Jonesy can see everything happening, but can do nothing. Pete finds Jonesy/Mr. Grey who forces him to direct and accompany him to Derry, after which Mr. Grey makes Byrus fungus constrict and kill Pete.
Henry convinces Army officer Owen Underhill to help him, revealing deep memories of the man through the telepathy gained from Duddits. Henry tells Underhill about Jonesy, that he thinks the alien is planning to infect the town's water supply with byrus, and that cold is fatal to the byrus, therefore infected people do not need to be executed. They form a plan.
Henry communicates telepathically with the byrus-infected captives, showing them that the Army intends to execute them. They panic and riot; many are killed attempting to escape, but most flee into the woods. Kurtz discovers the plan formulated by Henry and Underhill; he gathers a few of his men, and an officer infected with a byrum, and pursues Henry and the "rogue" officer Underhill.
Mr. Grey loses his way in the town, following old memories in place of the new ones stolen by Jonesy. Mr. Grey eventually becomes weak from hunger, not recognising what it is; Jonesy guides him to a diner to buy time.
Henry and Underhill make their way to Duddits, as Henry believes he is the only hope to defeat Mr. Grey; they find Duddits already packed up and ready to go as he knew they were coming. Duddits is very sick with leukemia; his mother is reluctant to let him go, but she accepts that Duddits needs to help his friends, and that he would be much happier dying in their company than dying alone in his room.
Mr. Grey eventually gets to the water supply for several cities in the area; Henry and Duddits confront him. Duddits uses his powers to force Henry and Jonesy into a place in which Mr. Grey, inside of Jonesy, will be vulnerable; he and Henry kill Mr. Grey. As Henry and Jonesy make their way back to their original bodies they find that Duddits has died from the combination of overusing his powers and leukemia. Outside, Kurtz finds Underhill and they are both killed. The byrum from the infected officer escapes but dies in the fire. The last of the alien byrus on earth dies.
Connections to other Stephen King Stories
Some of the novel takes place in Derry, a fictitious town featured in other works by King. A plaque dedicated to the Losers Club and graffiti saying "PENNYWISE LIVES" are direct references to one of these stories, the novel It. Both novels feature a group of young friends who must unite to defeat a force of great evil. The main catchphrase of the group of friends is 'SSDD' (same shit, different day) - a phrase used early on by Red in the film of the Shawshank Redemption.
There are a few connections to the Dark Tower series as well; since it is King's "master universe" it is frequently the medium through which connections are made between King's novels: As a child, Duddits lived on 19 Maple Lane, and the football jersey number of his childhood tormentor Richie Grenadeau (from whom Henry, Jonesy, Beaver, and Pete saved him) is also 19, appearing on Richie's jersey and the Derry Tigers shirt that Richie and his friends tore from Duddits in the parking lot. The number 19 is of great numerological significance in both Dark Tower series and the entire Stephen King universe. Also, the street where Duddits lives with his mother as an adult is named Dearborn. In the Dark Tower 4, Roland's assumed name is William Dearborn. Another main character from the Dark Tower series, Eddie, has a brother that is named Henry—a main character in this novel. The line, "o lost, a stone, a rose, an unfound door," appears in both Dreamcatcher and The Dark Tower. Enhancing other people's "special powers", such as what Duddits does, is something seen in the Dark Tower book 7 by Ted Brautigan.
A characters last name is mistaken for Henreid at one point. The name actually belonging to Lloyd Henreid from Stephan King's novel The Stand.
The story was adapted into a poorly recieved film in 2003, despite a highly praised ensemble cast.