The storyline concerns a growing, corrosive, alien amoeboidal entity that crashes to Earth from outer space inside a meteorite. It devours and dissolves citizens in the small community of Phoenixville/Downingtown, PA growing larger, redder, and more aggressive each time it does so, eventually becoming larger than a building.
In a small rural Pennsylvania town in July 1957, teenager Steve Andrews (Steve McQueen) and his girlfriend, Jane Martin (Aneta Corsaut), are kissing at a lovers' lane when they see a meteorite crash beyond the next hill; Steve decides to look for it. An old man (Olin Howland) living nearby finds it first. When he pokes the meteorite with a stick, it breaks open, and a small jelly-like blob inside attaches itself to his hand. In pain and unable to scrape or shake it loose, the old man runs onto the road, where he is nearly struck by Steve's car; Steve and Jane take him to Doctor Hallen (Stephen Chase).
Doctor Hallen anesthetizes the man and sends Steve and Jane back to locate the impact site and gather information. Hallen decides he must amputate the man's arm since it is being consumed. Before he can, The Blob completely consumes the old man, then Hallen's nurse, and finally the doctor himself, all the while continuing to grow. Steve and Jane return in time for Steve to witness the doctor's death. They leave and go to the police station and return with Lieutenant Dave (Earl Rowe) and Sergeant Bert (John Benson). There is no sign, however, of The Blob or its victims, and Bert dismisses Steve's story as a teenage prank. Steve and Jane are taken home by their parents, but they later sneak out.
In the meantime, The Blob consumes a mechanic at a repair shop and grows in size every time it consumes something. At the Colonial Theater, which is showing a midnight screening of Daughter of Horror, Steve recruits Tony (Robert Fields) and some of his friends to warn people about The Blob. When Steve notices that his father's grocery store is unlocked, he and Jane go inside. The janitor is nowhere to be seen. Then the couple are cornered by The Blob; they seek refuge in the walk-in freezer. The Blob oozes in under the door, but quickly retreats. Steve and Jane gather their friends and set off the town's fire and air-raid alarms. The townspeople and police still refuse to believe Steve. Meanwhile, The Blob enters the Colonial Theater and engulfs and devours the projectionist before oozing into the auditorium, consuming a number of the audience. Steve is finally vindicated when screaming people leave the theater in a panic.
Jane, Danny, and Steve become trapped in the diner, along with the manager and a waitress. The Blob, now enormous and blood red from the people it has consumed, has engulfed the building. Dave has a connection made from his police radio to the diner's telephone, telling those in the diner to get into the cellar before they bring down a live power line onto The Blob.
When the live wire lands, it discharges a massive electrical current into The Blob, but it is unaffected and the diner is set ablaze. When the diner manager uses a carbon dioxide extinguisher on the fire, Steve notices that this causes the Blob to recoil. Steve remembers that it also retreated from the freezer, saying "That's why it didn't come in the ice box after us. It can't stand cold"! Shouting in hopes of being picked up on the open phone line, Steve tells Dave about the Blob's vulnerability to cold. Jane's father, Mr. Martin (Elbert Smith), leads Steve's friends to the high school to retrieve the 20 fire extinguishers there. Returning, the brigade of fire extinguisher-armed students and police first drive The Blob away from the diner, then freeze it, saving Steve, Jane, and the others.
Dave requests authorities send an Air Force heavy-lift cargo aircraft to transport the Blob to the Arctic, where it is later parachuted to the ice and snow pack. Dave says that while The Blob is not dead, at least it has been stopped. To this, Steve Andrews replies, "Yeah, as long as the Arctic stays cold". ("The End" title card morphs into a question mark.)
The film was originally titled The Molten Meteor until producers overheard screenwriter Kay Linaker refer to the film's monster as "the blob". Other sources give a different account, saying that the film went through a number of title changes (the monster was called "the mass" in the shooting script) before the makers settled on The Glob. After hearing that cartoonist Walt Kelly had used The Glob as a title for his Pogo children's book, they mistakenly believed that they could no longer use that title, so they changed it to The Blob.
The Blob was directed by Irvin Yeaworth, who had directed more than 400 films for motivational, educational, and religious purposes. Though the budget was set at $120,000 it ended up costing only $110,000. Filmed in and around Valley Forge, Pennsylvania, principal photography took place at Valley Forge Studios. Several scenes were filmed in the towns of Chester Springs, Downingtown, Phoenixville, and Royersford, including the basement of a local restaurant named Chef's. For the diner scene, a photograph of the building was put on a gyroscopically operated table onto which cameras had been mounted. The table was shaken and the Blob rolled off. When the film negative was printed in reverse, it appeared to be oozing over the building. The Blob was filmed in color by De Luxe and widescreen.
28-year-old Steve McQueen received $3,000 for his starring role. He turned down an offer for a smaller up-front fee in return for a 10% percent share of profits, thinking that the film would never make money; he needed his signing fee immediately to pay for food and rent. However, The Blob ended up a hit, grossing $4 million at the box office.
The film's tongue-in-cheek title song, Beware of The Blob, was written by Burt Bacharach and Mack David and became a nationwide hit in the U.S., peaking at number 33 on the Billboard chart on 9 November, 1958. The song was recorded by studio group the Five Blobs (actually singer Bernie Knee overdubbing himself). Though legend has it that the opening novelty song was composed by a young and unknown Burt Bacharach, along with Bacharach's famous songwriting partner, Hal David, David's brother Mack composed the lyrics and by that time Bacharach had already achieved some measure of success when the film was released.
The background score for The Blob was composed by Ralph Carmichael. It was one of just a few film scores that Carmichael wrote. Carmichael is best known for his musical associations with Billy Graham and for arranging The Magic of Christmas for Nat King Cole. Carmichael also composed the original theme for the film, entitled "Violence" on the soundtrack album, which started the film on a serious and frightening note. It was against the director's wishes to replace the original theme song with that by Bacharach/David. However, because the latter encourages audiences to view The Blob as campy fun, it has contributed to the film's enduring popularity. Both Carmichael's score and Bacharach/David's song were released in 2008 by the Monstrous Movie Music soundtrack label.
According to Tim Dirks, the film was one of a wave of "cheap teen movies" released for the drive-in market. They consisted of "exploitative, cheap fare created especially for [young people] in a newly-established teen/drive-in genre."
The Blob was released theatrically in 1958 on a double bill with I Married a Monster from Outer Space.
When The Blob first premiered as the B film of the double bill with I Married a Monster from Outer Space, it was quickly moved up to be the main feature. While audiences liked it, critics were not as kind. The review in The New York Times highlighted some of the problems and identified some positives, although Steve McQueen's debut was not one of them. Concentrating on director Irvin Yeaworth's work, "Unfortunately, his picture talks itself to death, even with the blob nibbling away at everybody in sight. And most of his trick effects, under the direction of Irvin S. Yeaworth Jr., look pretty phony".
The review continued with, "On the credit side, the camera very snugly frames the small town background — a store, a church spire, several homes and a theatre. The color is quite good (the blob rolls around in at least a dozen horrible-looking flavors, including raspberry). The acting is pretty terrible itself, there is not a single becomingly familiar face in the cast, headed by young Steven McQueen and Aneta Corseaut."
Variety had a similar reaction, seeing McQueen as the star, gamely "giving the old college try" but that the "... Star performers, however, are the camerawork of Thomas Spalding and Barton Sloane’s special effects".
The film review aggregator Rotten Tomatoes records that reviewers give The Blob mixed-to-positive reviews, earning an approval rating of 66%. The "critics" consensus states: "In spite of its chortle-worthy premise and dated special effects, The Blob remains a prime example of how satisfying cheesy B-movie monster thrills can be".
The Blob has been released as part of the Criterion Collection on three formats. First in 1988 on LaserDisc, then in 2000 on DVD, and in 2013 on Blu-ray. The film, together with Son of Blob, was released on DVD in Australia by Umbrella Entertainment in September 2011. The DVD is compatible with all region codes and includes special features such as audio commentaries with Jack H. Harris, Bruce Eder, Irvin Yeaworth, and Robert Fields. In November 2016, Umbrella released a 2-disc Blu-ray titled The Blob Collection, featuring the 1988 version of The Blob on disc one, and the 1958 version and Son of Blob on disc two. Disc two plays the Criterion Collection's opening identification, although the release was distributed by Umbrella Entertainment with no mention of Criterion on the disc sleeve.
A sequel, Beware! The Blob, was made in 1972, directed by Larry Hagman. Home video releases used the tagline "The Movie That J.R. Shot", in reference to his character's near-demise in the television series Dallas.
In 1988, a remake of the same name was made, and directed by Chuck Russell.
In August 2009, it was revealed that musician-turned-director Rob Zombie was working on another remake, but is no longer working on this project. In January 2015, Zombie was replaced by Simon West to direct the remake. It was announced that the film would be produced by Richard Saperstein and Brian Witten, together with the producer of the original, Jack H. Harris, as executive producer.
Since 2000, the town of Phoenixville, Pennsylvania, one of the filming locations, has held an annual "Blobfest". Activities include a re-enactment of the scene in which moviegoers run screaming from the town's Colonial Theatre, which has recently been restored. Chef's Diner in Downingtown is also restored, and is open for business or photographs of the basement on weekday mornings only.
The Blob itself was made from silicone, with increasing amounts of red vegetable dye added as it "absorbed" people. In 1965, it was bought by film collector Wes Shank, who has written a book about the making of The Blob.
According to Jeff Sharlet in his book The Family, The Blob was "about the creeping horrors of communism" only defeated "by freezing it — the Cold War writ small and literal". Rudy Nelson, one of the scriptwriters for the film, has denied many of Sharlet's assertions, saying "What on earth can Sharlet say about the movie that will fill 23 pages—especially when what he thinks he knows is all wrong"?
Film historians Kim R. Holston and Tom Winchester noted that the film was "Filmed in southeastern Pennsylvania at Valley Forge Studios, (and) this very famous piece of pop culture is a model of a decent movie on a small budget".
The film is recognized by American Film Institute in these lists:2001: AFI's 100 Years...100 Thrills – Nominated
2003: AFI's 100 Years...100 Heroes & Villains:
“The Blob” – Nominated Villain