Picking up 15 years after the events of the first Blob movie, an oil pipeline engineer and geologist named Chester Hargis (Godfrey Cambridge) returns to his suburban Los Angeles home from a three-month excursion to Alaska near the North Pole, bringing with him a small sample of a mysterious frozen substance uncovered by a bulldozer on a job site... an off-camera story which he tells his wife Marian (Marlene Clark). Not aware that the substance is a piece of the Blob from the original 1958 incident in Pennsylvania, Chester stores the substance in a small metal container in his home freezer prior to taking in to the laboratory to be analyzed. When Marian takes the metal container out of the freezer and leaves it unattended on the kitchen counter, both she and Chester forget about it since Chester is planning to go away on a week-long fishing trip which he has stored several cans of beer in his fishing container. With both Chester and Marian distracted by their bickering, the substance thaws out and a red gelatinous substance oozes from the metal canister after consuming a small house fly. The small blob then quietly engulfs their pet kitten. Seemingly energized by the sustenance, the blob oozes out into the back yard, where Marian is searching for the kitten. As the creature grasps Marian's legs to engulf her, she faints in terror and succumbs, unknown to Chester, who is watching television in the living room. Soon after, family friend Lisa Clark (Gwynn Gilford) enters the house to find Chester sitting in his reclining chair being dissolved/digested by the ever-expanding blob. Horrified, Lisa races to her boyfriend Bobby Hartford (Robert Walker Jr.) at his farm for help, but when they return to the Hargis house, no evidence of the tragedy remains.Meanwhile, bowling alley owner Edward Fazio (Richard Stahl), having spotted Lisa speeding, reports her to the police and follows her to Chester's house to admonish her. When Lisa tries to explain to the police that her friends are missing, they search the house while Mr. Fazio insists that they arrest her for speeding. After finding nothing suspicious, the police release Bobby and Lisa.Elsewhere, two teenagers, a guitar playing hippy named Randy (Randy Stonehill) and his girlfriend (Cindy Williams), are smoking marijuana in a storm drainage culvert, when policeman Zed (Sid Haig) confronts them. When Deputy Ted Sims (Ted Baar) arrives and tells Deputy Zed to report back to the police station, he tells the two teenagers that they are under arrest for possession of a controlled substance. Seeing the red, viscous material dripping into the culvert behind Deputy Sims's head, the teenagers warn the policeman, but he suspects they are trying to trick him and ignores their pleas. Within seconds, the blob engulfs Sims and the teenagers.Later that evening, the blob seeps into a hair salon through the sewer system, swallowing the customer's head (John Houser) and hairdresser's arms (Shelley Berman) during a shampoo at the sink.Meanwhile, Bobby and Lisa return to her house, where dozens of Bobby's friends are waiting to throw him a surprise birthday party. As the festivities ensue, Lisa, upset that Bobby does not believe her story, asks him to take her to his ranch.In another part of town, a middle-aged Russian man (Tiger Joe Marsh) is taking a bath when the blob slips under the door and swallows his pet dog as the man watches helplessly. Petrified and naked, the man runs into the street, where police pick him up for exposing himself. Back at the police station, reports of missing persons are piling up, including a group at a bar that the blob consumes (off-camera).Boy Scout Taskmaster Adleman (Dick Van Patten) is with his troupe hiking through the area and observing the events that are unfolding around them. Adleman becomes a victim himself (off-camera) when he confronts the blob in a field near the late Chester's house, but most of his fellow Boy Scouts escape.At Bobby's ranch, the blob, having already consumed three hobos (Larry Hangman, Burgess Meredith and Del Close), is growing exponentially after consuming live chickens and possibly some livestock, and quickly envelopes Bobby's truck when the couple arrives. Knowing what fate awaits them, Lisa screams for help, but they cannot escape. Suddenly during the tumult, the blob recedes for no apparent reason.Bobby and Lisa race to a gas station (where the Blob has apparently been and consumed, off-camera, the attendant and an unknown number of patrons) to call Sheriff Jones (Richard Webb) and are told that he is at the bowling tournament. Seeing their friend Joe (Gerrit Graham) and his girlfriend Leslie (Carol Lynley) driving by, Bobby and Lisa describe the horrific monster. Although Leslie is convinced of their sincerity, Joe mocks them in disbelief and drives off in his dune buggy to investigate their claims.As Bobby, Lisa and Leslie make their way to the town bowling tournament to find the sheriff, they are confronted by the blob, which has covered the road and is enveloping Joe and his car. A hysterical Leslie rushes to help Joe, but dies with Joe under the oozing mass.Taking an alternate route, Bobby and Lisa reach the bowling alley, where Bobby uses the loudspeaker to advise everyone to leave the area, but his warning goes unheeded. Angered by the disruption, Fazio orders his bouncer to bring Bobby and Lisa to his office, where they explain the danger. Meanwhile, the blob, having already devoured the bowling alley mechanic, surges down all the lanes toward the terror-stricken people, who run for their lives.Bobby, Lisa and Fazio barricade themselves in a broadcast booth high above the adjacent ice rink, which is closed for repairs, and watch as dozens of people succumb to the fast-flowing blob. Using the speaker system, Bobby tells the sheriff and his men, who are waiting outside, that the blob is a giant single-celled animal that can ooze through cracks. As the sheriff and his men dress in riot gear to prepare to attack the creature, Bobby tries to electrocute it with a live wire, but does not succeed. Jones and his deputy shoot at the creature, which is unharmed and subsequently eats the deputy.Having devoured the remaining public in the facility, the blob seeps into the booth through a hole in the floor. Scrambling to get away from the creature, Bobby knocks over a small refrigerator and spills ice onto the blob, which shrinks from the cold. Realizing that the air conditioner in their truck must have been the reason the blob did not eat them earlier, Bobby and Lisa asks Fazio how to cool the rink to freeze the blob. Meanwhile outside, the sheriff, having lost contact with Bobby, assumes that he and the others have been eaten, and orders his men to dowse the building in gasoline so they can burn the blob, unaware that fire will have little effect on the creature. Inside, Bobby heroically climbs the ropes leading to the rink's switch box. Once the rink's cooling system is on, the blob freezes solid instantaneously.Bobby then runs out of the building just in time to stop the sheriff from setting it ablaze. Minutes later, the sheriff proudly stands on top of the mounds of the frozen blob to give a television interview about the shapeless monster that almost destroyed their town and possibly the world. Just under his feet, a small section of the blob defrosts from the camera light and begins to engulf the sheriff's boot.....THE END?