Allie Fox, is a brilliant but stubborn inventor who has grown fed up with the American Dream and consumerism. Furthermore, he believes that there is a nuclear war on the horizon as a result of American greed and crime. After Allie and his eldest son Charlie acquire the components at a local dump, he finishes assembling his latest creation, an ice machine known as Fat Boy. Allie's boss, Mr. Polski, an asparagus farm owner, complains that Allie is not tending to the asparagus, which is rotting. Allie, Charlie, and Allie's youngest son, Jerry, meet Mr. Polski, and Allie shows him "Fat Boy." The machine leaves Polski unimpressed. As he drives past the fields, a dejected Allie comments on immigrants picking asparagus, and says that where they come from, they might think of ice as a luxury.
The next morning, Allie throws a party for the immigrant workers before telling his family that they're leaving the United States. On board a Panamanian barge, the family meets Reverend Spellgood, a missionary, his wife, and their daughter, Emily. Allie and the Reverend clash due to their opposing religious views. When the barge docks in Belize City, the families disembark and go their separate ways. Allie purchases a small village called Jeronimo in the rainforest along the river from a drunk German.
Mr. Haddy takes Allie and his family upriver to Jeronimo. Allie meets the inhabitants and proceeds to start building a new, 'advanced' civilization, in the process inventing many new things. The locals take kindly to Allie and his family, but Allie's will to build a utopian civilization keeps them working to their limits. Reverend Spellgood arrives to convert Jeronimo's citizens. In the process, Allie and Spellgood angrily denounce each other, leading to a permanent schism: Allie believes Spellgood to be a religious zealot; Spellgood believes Allie to be a communist. Allie sets to constructing a huge version of "Fat Boy" that can supply the town with ice. Upon completing the machine, Allie hears rumors of a native tribe in the mountains that have never seen ice. Allie recruits his two sons to carry a load of ice into the jungle to supply the tribe. Upon arriving, Allie finds that the load has melted, and that the tribe has already been visited by missionaries.
When Allie returns to Jeronimo, he learns that Spellgood has left with much of the populace, scaring them with stories of God's biblical destruction. The near-empty town is visited by three rebels, who demand to use Jeronimo as a base. Allie and his family agree to accommodate them while Allie constructs a plan to be rid of them. Set on freezing them to death, Allie bunks the rebels up in the giant ice machine, tells Charlie to lock its only other exit, and activates it. The rebels, waking in panic, try to shoot their way out. To Allie's horror, the rebels' gunfire sets off an explosion within the machine. By the next morning, both the machine and the family's home is in ruins, and chemicals from the destroyed machine have severely polluted the river.
Forced downstream, Allie and his family arrive at the coast. Mother and the children rejoice, believing they can return to the United States. Allie, refusing to believe his dream has been shattered, announces that they have all they need on the beach and tells them that America has been destroyed in a nuclear war. Settling on the beach in a houseboat he has built, and refusing assistance from Mr. Haddy, Allie believes that the family has accomplished building a utopia. One night, the storm surge from a tropical cyclone nearly forces the family out to sea until Charlie reveals that he has been hiding motor components given to him by Mr. Haddy, allowing them to start the motor on the boat.
Forced to travel upstream once again, Charlie and Jerry grow resentful of their father. Coming ashore when the family stumbles across Spellgood's compound, Allie sees barbed wire, and mutters that the settlement is a Christian concentration camp. While the rest of the family sleeps, Charlie and Jerry sneak over to the Spellgood home. After finding out that the United States was not destroyed and that Emily will assist them in escaping from Allie. Before Charlie can persuade Mother and his sisters to leave, Allie sets Spellgood's church on fire. Spellgood shoots Allie, paralyzing him from the neck down. The family escapes aboard the boat.
The family begins traveling downriver again, with Allie drifting in and out of consciousness. Allie asks his wife if they are going upstream. She lies to him for the first time. Charlie's narration reports the death of Allie, but gives hope that the rest of the family can live their lives freely from now on.Harrison Ford as Allie Fox
Helen Mirren as "Mother" Fox
River Phoenix as Charlie Fox
Conrad Roberts as Mr. Haddy
Andre Gregory as Reverend Spellgood
Martha Plimpton as Emily Spellgood
Melanie Boland as Mrs. Spellgood
Dick O'Neill as Mr. Polski
Jadrien Steele as Jerry Fox
Hilary Gordon as April Fox
Rebecca Gordon as Clover Fox
Alice Heffernan-Sneeds as Mrs. Polski
Jason Alexander as Hardware Clerk
William Newman as Captain Smalls
Aurora Clavel as Mrs. Maywit
Butterfly McQueen as Mrs. Kennywick
Producer Jerome Hellman bought the rights to Theroux's novel as soon as it was published, and Weir committed to filming it. Jack Nicholson was originally offered the lead role, but backed out partly because he could not watch Los Angeles Lakers games in Belize, where part of the film was to be shot. He instead went on to star in Terms of Endearment, a role Ford had also been offered.
As the film went into pre-production, and Weir was in Central America scouting for locations, the financial backing for the film fell through and the project was suspended indefinitely. In the meantime, Weir was approached to direct Witness starring Harrison Ford. The film, which was Weir's first American production, was a critical and commercial success, garnering eight Academy Award nominations including Weir for Best Director, Ford for Best Actor, and the film itself for Best Film. During the production of Witness, Weir discussed The Mosquito Coast with Ford who became interested in the role of Allie Fox (though Ford's agent was less enthusiastic). With Ford attached to the project, financial backing and distribution for the film was easier to find (ultimately from Saul Zaentz and Warner Bros.).
Filming began the week of February 7, 1986 in Belize and finished there on April 26 before moving to Georgia. Weir and Ford famously missed the Academy Awards ceremony for which they had both been nominated for Witness, which won two Oscars, for Best Screenplay and Best Film Editing.
The film contains the last feature film role of Butterfly McQueen, who had a prominent role in Gone with the Wind. She plays a lapsed churchgoer, and in real life was a vocal atheist. The film also features a brief appearance by Jason Alexander. River Phoenix and Martha Plimpton started dating after the two met while making this film; the relationship lasted for several years, during which they also co-starred in Sidney Lumet's Running on Empty. It was also his performance as the son to Harrison Ford's character that led Ford to recommend Phoenix to Steven Spielberg for the part of teenage Indiana Jones in Indiana Jones and the Last Crusade.
The film was initially a critical and commercial disappointment, but has since received much stronger modern reviews. Film review aggregator Rotten Tomatoes gives the film a positive score of 75% based on a sample of 20 reviews, with an average rating of 6.4 out of 10. Siskel & Ebert were split, Siskel giving the film a "thumbs up" and Ebert giving it a "thumbs down," criticizing Allie Fox for being "boring." However, he did compliment Ford's performance. Vincent Canby of The New York Times called it "utterly flat." In her review for The Washington Post, Rita Kempley wrote, "Sooner or later a man of invention will pollute paradise, a grand contradiction that gives Mosquito its bite and Ford inspiration for his most complex portrayal to date. As a persona of epic polarities, he animates this muddled, metaphysical journey into the jungle." In her review for the Los Angeles Times, Sheila Benson wrote, "He's orchestrated The Mosquito Coast's action to match Fox's progressive mental state, from rage to explosion to squalls and finally to hurricane velocity; however, the film leaves us not with an apotheosis, but exhaustion." In his review for The Globe and Mail, Jay Scott wrote, "The Mosquito Coast is a work of consummate craftsmanship and it's spectacularly acted, down to the smallest roles ... but its field of vision is as narrow and eventually as claustrophobic as Allie's." The negative reviews the film received prompted Harrison Ford to defend the film in the media: "there have been mixed reviews and I think the film has been very unfairly treated in some quarters. I have never seen a serious film treated so badly by the critics. And I think they're wrong. I don't mind saying I'm here trying to counter those negative reviews ... I'm not defensive about the picture, but I want the public to hear another point of view. Critics see a film and then rush to review it. This is the sort of movie that really doesn't sink home for about three days. It is disturbing and makes you think. It stays with you."
With a production budget of $25 million, the film made a little over $14 million in North America. Despite being one of his least commercially successful films, Ford has defended it, saying in a 1992 interview:
It's the only film I have done that hasn't made its money back. I'm still glad I did it. If there was a fault with the film, it was that it didn't fully enough embrace the language of the book (by Paul Theroux). It may have more properly been a literary rather than a cinematic exercise. But I think it's full of powerful emotions.