Description
The film opens with a sequence of meteor showers, with a narrator describing that meteorologists and scientists are studying the phenomenon. With the meteor shower ongoing, a watchman is seen entering the botanical gardens' greenhouse, where the first sighting of Triffids occurs as they are still small plants.
Triffids are tall, carnivorous, mobile plants capable of aggressive and seemingly intelligent behaviour, which arrived on Earth as spores from a meteor shower. They move about the countryside by "walking" on their roots, appear to be able to communicate with each other, and possess a deadly whip-like venomous sting that enables them to kill their victims and feed on the corpses.
The scene transitions to a hospital, where Bill Masen (Howard Keel), a merchant navy officer, is lying in hospital with his eyes bandaged as he's waited on by a nurse named Ms. Jamieson (Colette Wilde). Masen discovers that while he's been waiting for his injured eyes to heal, an unusual meteor shower has blinded most people on Earth.
After nurse Jamieson turns off the light's in Masen's hospital room, the scene cuts to a lighthouse on an island off Cornwall, where Tom Goodwin (Kieron Moore), a flawed but gifted scientist and his wife Karen (Janette Scott), are arguing. They decide to leave the lighthouse in the morning because Tom appears fed up with his wife and his work.
Masen wakes up in the hospital the next morning to find the hospital deserted. Masen gets startled as a blind Dr. Soames comes up from behind him and asks Masen to take him to his office where Masen tests Dr. Soames' eyesight. Dr. Soames tells Masen that a majority of the people have been blinded by the lights of the meteor shower the night prior. Dr. Soames then sends Masen away on an errand so he can jump out of his office's window to commit suicide.
Tom and Karen Goodwin are still in the lighthouse on Cornwall preparing to leave, when the radio announcer requests that everyone who has retained their sight should head to the dockyard since most Navy personnel have not been blinded and are there to help. The message continues to explain that mobile plants with a killer stinger are moving around England and warns everyone to be safe before the broadcast ends.
Masen heads to the tracks just as a train comes barreling down the tracks and crashes at the station. Chaos erupts as blind people come pouring out of the train and people on the platform start running around while tripping over everyone else. An orphaned schoolgirl named Susan (Janina Faye) gets off the train and starts getting crowded and grabbed by blind people who want her help when Susan admits she can see. Masen sees Susan struggling and rescues her.
On the way to Masen's ship, Masen steals a car that's been crashed up onto the curb. Masen and Susan are driving through fog when they reach a roadblock of crashed and abandoned cars. While trying to pass the cars, the car's rear tire gets stuck in some mud. As Masen and Susan go off to dig for rocks to give the tire traction, a Triffid begins slinking towards Susan. Susan makes it back to the car where Masen manages to free the tire after slamming the gas pedal down repeatedly. Masen and Susan speed away from the Triffid, just as it spits a green substance on their rear window.
Masen and Susan finally make it to the dockyard where Masen's ship resides. In the radio control room of the ship, Masen and Susan are changing the channels to find out the tragedy of London has befallen the rest of the world as well. One of the first few stations is from out on the ocean, hundreds of miles from New York on the SS Midland, and another from Flight 365 from Cape Town.
While in the radio control room, Masen and Susan's perusing of radio channels gets interrupted by Flight 365 crashing at the dock right in front of the ship. The two of them leave the ship.
Back at the lighthouse, Karen alerts her husband Tom of a Triffid growing on a ledge. After seeing nothing outside, Tom and Karen turn around and head back inside only to come face to face with a fully grown Triffid. Tom battles the Triffid, stabbing it with his spear, as the Triffid's tentacle limbs reach out and attack him. Tom manages to knock the head off of the Triffid, which causes the whole plant to seemingly wilt and die.
Masen and Susan cross the English Channel into France, where they come across Christine Durant (Nicole Maurey) with a blind child standing in the storm out in the middle of the road. Miss Durant gives Masen directions as he drives them all to a chateau where they meet siblings Mr. Coker (Mervyn Johns) and Miss Coker (Alison Leggatt). The Cokers have been giving dozens of blind people shelter at their chateau where he they welcome Masen and Susan to take refuge. The nurse leaves Susan with an English-speaking French woman named Bettina (Carol Ann Ford).
Tom and Karen have been dissecting and studying their Triffid all day when they decide to go to bed. Karen is awoken by a crashing sound, and looks down over the stair railing to see the Triffid moving around downstairs. Tom wakes up to Karen screaming and goes downstairs to investigate. He sees his lab torn up and the table holding the Triffid is overturned with the Triffid nowhere in sight. Karen realizes the Triffids can regenerate since it was able to escape the lighthouse. With the Triffid outside, Tom boards up the lighthouse, trapping himself and Karen inside.
Masen leaves the chateau to gather supplies from a local grocery store with Mr. Coker, when the encounter a Triffid. The two of them follow the Triffid to the meteor landing site where they see a patch of Triffid plants growing before their eyes. The two of them rush back to the chateau to warn the others. Before Masen and Mr. Coker can build their case for leaving the chateau, Susan leads the men and Miss Durant outside to where an airplane she heard earlier is making a second pass overhead. The plane goes down and Masen and Mr. Coker get in the car to investigate the crash site.
At the site of the plane crash, Triffids begin coming out of the foliage and overrun the car, so Mr. Coker and Masen are forced to escape on foot. Masen carries Mr. Coker out to a clearing after Mr. Coker twists his ankle during the escape, only for Mason to discover Mr. Coker died after being sprayed by a poisonous gas from a Triffid they passed on the way.
Masen walks back to the chateau alone to find a party being held by escaped convicts who still have their sight. The convicts are holding everyone captive and forcing them to party with them. Masen rescues Miss Durant and Susan from the party. As they leave the chateau, Masen sees Bettina being overtaken by Triffids, but shooting does nothing and the three of them are forced to escape in the convicts' prison bus as the chateau and everyone inside is overrun by Triffids. They arrive in a post-apocalyptic Toulon. Masen says there is an American naval base in Cadiz, Spain that they have to get to next.
Masen, Susan and Miss Durant arrive in Spain and stop for a rest at a carnival, where Susan finds a musical clown car. The trio drive to a Spanish villa where they meet the blind couple Mr. Luis de la Vega (Geoffrey Matthews) and his pregnant wife Teresa (Gilgi Hauser), who has already been blind for years. Luis tells Masen that the Cadiz naval base has been evacuated by submarines since those who were underwater didn't get blinded by the meteor shower.
Masen gets Luis' radio transmitter working just in time to hear the navy broadcasting a message about the final survivor pickup the next day, Saturday, in Alicante. The group decides to leave early in the morning, and Masen electrifies the enclosing fence around the villa to keep Triffids out during the night. Meanwhile, in one of the bedrooms, Teresa gives birth to a boy.
As night falls, a huge number of Triffids arrives and are being held back by just the fence. The current is too weak to hold the Triffids for long and the shocks of electricity do little harm. Masen, with Miss Durant's help, turns the hose from an oil tanker truck into a flamethrower to set the Triffids on fire. The hoards of Triffids are still at the fence, waiting. It's realized that the Triffids are attracted to sound since they keep coming despite being attacked.
The following morning, Masen uses the musical clown car to lure the Triffids away from the villa so Susan, Miss Durant, and Mr. and Mrs. de la Vega and their son can escape and drive to Alicante (in the de la Vega's own car). The group makes it into a navy submarine and Masen, after abandoning the clown car in a group of Triffids, makes it onto a navy lifeboat and joins the rest of the group on the submarine.
In the lighthouse, the Triffids break through the boards and make their way inside. The Triffids corner Tom and Karen at the top of the stairs with their only escape being a window looking out at the jagged cliffs and ocean below. In a last ditch effort, Tom sprays the Triffids with a salt-water fire hose, and the Triffids begin dissolving into a cloud of green smoke. Tom realizes that sea water was the answer they have been looking for all along, and uses the hose to kill the rest of the Triffids in the lighthouse.
The narrator states that humanity has conquered the Triffids by turning to the very thing that gave humans life in the beginning: sea water. Meanwhile, the people from the submarine have disembarked and are heading into a steeple as they prepare to give thanks for their survival.
