Plot summary

Off the Florida coast, a ship dumps dozens of barrels clearly marked "Danger Radioactive Waste" into the water. Later, the barrels wash ashore on an island where the contents ooze onto the sand, contaminating a group of ants.Meanwhile, real-estate developer Marilyn Fryser greets prospective buyers boarding a yacht for a day cruise to visit her latest project, Dreamland Shores. Already aboard are Dan Stokely, the ship's captain, his first mate Jim, and Marilyn's salesman, Charlie Pearson, with whom she is having an affair. At the yet-to-be-built Dreamland Shores, two workers prepare for the visitors by setting up a tent with tables on the beach not far from where the radioactive waste has contaminated the ants. Once they arrive, Marilyn's nine guests get to know one another: Coreen Bradford, a young woman recovering from a relationship with a married man; Margaret Ellis, an executive secretary; a young married couple, Larry and Christine Graham; a middle-aged couple, Thomas and Mary Lawson; an elderly couple, Harry and Velma Thompson; and a brooding young man, Joe Morrison.Charlie and Marilyn take their guests on a two-hour tour of the property, pointing out where the future marina, tennis club, and golf course will be. When the party stops at another tent for refreshments, Marilyn is annoyed that the workers have gone. Suspicious, Thomas wanders off and just as he discovers that some pipes are merely a facade, he and Mary are attacked and killed by giant ants.Back on the tour, the group realizes that Thomas and Mary are missing. Marilyn hears a loud buzzing noise, but dismisses it. When they discover the body of one of the workers, Joe decides to go looking for Thomas and Mary. Coreen is the only one brave enough to go along. They discover Thomas' bloody remains. Everyone returns to the beach where they see a line of the giant ants marching toward their moored ship. Dan and Jim battle the ants with an ax. A gasoline can ruptures and the ship explodes, killing Jim. Dan swims back to shore. As night falls, the group builds a fire to ward off the ants.In the morning, a storm hits, extinguishing their ability to rebuild the fire. Although Charlie suggests escape in a rowboat lying at the mouth of a river two miles away, Marilyn wants to await rescue at a deserted beach house. She is only convinced to join the others when she sees the house is infested with ants. Moving through the jungle toward the river, the party encounters a group of ants and is forced to run. The elderly Thompsons cannot keep up and take shelter in a shed. Christine trips and hurts her ankle, but Larry refuses to help and leaves her behind to be devoured. When Marilyn snags her sweater on a tree, Charlie helps her, but the ants get and eat him too as she escapes. Dan, Margaret, Marilyn, Joe, Coreen, and Larry reach the river and find the rowboat. Meanwhile, the Thompsons emerge from the shed to find themselves surrounded by ants (who presumably eat them too).As Dan rows the boat, the others lament their fate. At a fork in the river, Larry insists they go left, but they soon hear the buzzing of the ants. The ants attack from overhanging branches, and Dan and Joe fight them off with oars. Dan turns the boat back toward the fork; however, an ant attacks Larry, and the boat capsizes, knocking the others into the water. The five survivors swim to shore and proceed on foot along the river. Marilyn argues with Dan and stalks off, but soon comes face-to-face with an ant, and rejoins the group. Coreen and Dan realize the ants are herding them upstream, but they have no alternative.Eventually, the group comes upon a house barricaded with barbwire. Sam and Phoebe Russell, the couple that lives there, call the local sheriff and Phoebe whispers something to Coreen. Sheriff Art Kinkade drives them to a motel in a small town near a sugar refinery. The proprietor, Anson Parker, who is also the town's mayor, is on the phone long-distance demanding more sugar for the refinery. Coreen tells Marilyn and Margaret that the old woman told her, "Whatever you do, don't let them take you to the sugar refinery."Joe uses a payphone to call a friend in the capitol, but is told the lines are down. Dan finds that strange since the mayor was talking long distance. While the women clean up, Dan and Joe go to rent a car. When the girl at the rental office stalls them, they realize the townspeople are conspiring to keep them there. Dan and Joe hot-wire a car and the five attempt to leave town, but they hit a police roadblock. Joe tries to run past the checkpoint, but the car pitches into the river. Pulled to safety, Joe and Coreen escape into the sugar cane fields, but Dan, Margaret and Marilyn are captured and taken into custody to the refinery.Inside the refinery, the sheriff explains that people line up each week so the queen ant can spray them with pheromones, which trigger an involuntary response in the humans to do the ants' bidding. In the field, Joe and Coreen are captured by deputies and brought to the others. Marilyn is forced into the booth with the queen ant, sprayed, and emerges espousing obedience. Dan enters the booth and fends off the queen ant with a lit flare. The worker ants then attack the humans. Joe opens the spigots on a fuel truck, and drives around the facility, leaving a flammable trail. The sheriff shoots the queen ant, but it attacks and kills Marilyn before it dies. Joe leaps from the truck, which crashes into the warehouse, bursts into flames, and incinerates the ants inside. Joe and the other survivors find a motorboat and escape.