The story starts 30 years ago when an exploration team excavates an entrance under a stone church in the Carpathian Mountains, and as they enter in a rockslide traps the explorers under the church, never to be heard from again. 30 years after that, a team of researchers led by Dr. Nicolai and his assistant, Dr. Kathryn begin to explore the area where the exploration team disappeared. Eventually they find access under the church in an underground river, and a group of experienced divers join the two doctors in exploring further. As they progress along and begin to go deeper and deeper into the earth, Dr. Nicolai learns of the legend regarding the Church, which was built to seal something evil under it, and that Templar Knights would venture into these caves to fight horrid human-like winged demons.
As the research team goes deeper and deeper into the cave, eventually one of the divers is attacked by one of the more carnivorous inhabitants of the cave and causes his breathing apparatus to explode, collapsing the way out of the cave and trapping everybody one mile under, unable to go back and forced to go deeper into the cave in an attempt to get out.
As they go deeper, they discover more of these atrocious winged monsters, and they begin to attack them and killing them off one by one while the team attempts to defy yawning underground chasms, powerful underwater currents, and each other as they begin to learn more sinister things about each other and question whether or not they can trust each other as something begins to develop in their team mates...
At its base, The Cave was a very good stand alone movie, and while it was released at the same time as a couple other movies with similarities (such as The Descent and The Cavern), the movie was able to develop a cult following.
Tropes that can be found in The Cave:
- Action Girl: Charlie shows some of this, especially while fighting the creature that attacks her while climbing.
- Artistic License – Chemistry: One character says he can smell methane gas - which is a colourless and odourless substance. Might be not the case. Said character is already mutated by the parasite, which heightened his senses. And if methane is a common hazard in the cave, the parasite would need to make its host capable of sensing and avoiding that hazard.
- Alien Blood: The bat-monsters have pink blood.
- Bizarre Alien Senses: The creatures "see" via echolocation.
- Black Dude Dies First: Averted. The Asian is one of the last characters to die and the black guy survives.
- Bunny-Ears Lawyer: The caving team are quite quirky but very good. As Jack puts it when they're trapped, the people best qualified to get them out of the cave-in are all currently down there.
- Covers Always Lie: No, the team is not attacked by a massive subterranean water monster. While there are monsters and they do travel through water as well, they're human-sized.
- Creepy Cave: The setting of the film is a massive uncharted cave system. Parts of it are underwater, parts are frozen, and parts have fires burning inexplicably—this being a horror film, all are played as unsettling if not downright terrifying. And then there are the things that live in them . . .
- Creepy Monotone: Jack as the virus starts to spread.
- Downer Ending: Everyone except Tyler and Top are dead, while Katheryn is infected and reveals that the creature wanted to escape the cave all along. The last we see of her is disappearing into a crowd of people.
- Due to the Dead: Charlie's body gets treated with sad respect.
- Dwindling Party: By the end only Top, Tyler and Katheryn have survived. And Katheryn is revealed to have the infection.
- Face–Monster Turn: One of the explorers, after being attacked by one of the subterranean monsters, begins to start mutating into one of them, his eyes changing into a different shape while also being able to detect the monsters in complete darkness as well. Subverted in that he's able to retain control of himself until sacrificing himself to let the other three escape.
- Five-Token Band: We have the two white American brothers, the black guy, the female tomboy, the Canadian and the Australian on the diving team. The expedition also includes the east European doctor, the British female scientist and the Asian camera man.
- Gosh Dang It to Heck!: Charlie when she realizes "They fly, they freaking fly!" Intended to be a Precision F-Strike, but the studio was gunning for a specific rating.
- Heroic Sacrifice: Jack blows up the last cavern while fighting one of the monsters to give the other survivors an opportunity to escape.
- Briggs, remaining behind to provide cover as Katheryn and Alex run.
- Implied Love Interest: There appears to be an attraction between Tyler and Katheryn.
- Improbable Age: Subverted. Katheryn's youth is justified by her being the associate to Dr Nikolai - who is in charge. And Lena Headey was 32 at the time, making her a little more plausible than many other such scientist babes.
- Informed Attribute: Strode being a military veteran is only mentioned after his death and it certainly didn't help him much when he was attacked.
- Leg Focus: Charlie's legs are highlighted when she strips down to a halter top and short shorts for her climb.
- Mutual Kill: Charlie is mauled by one of the creatures and dies, but not before managing to light it on fire and kill it at the same time.
- Oh, Crap!: Charlie has two in rapid succession, first when she encounters one of the creatures up close and sees it has More Teeth than the Osmond Family, and second when she realizes the creature can fly!
- Ragtag Bunch of Misfits: The diving team of course. But they've all been together long enough that they're genuinely good at what they do.
- Rodents of Unusual Size: The discovery of a spaniel-sized albino gopher provides an early sign that the parasite can mutate mammals, adapting them to the cavern environment.
- Russian Guy Suffers Most: Nicolai does not have it easy.
- Scary Scorpions: Our cast encounters albino ones in one of the smaller tunnels.
- Shown Their Work:
- The movie is inspired by true events. Around 35 new species were discovered in Eastern European caves in the 1980s. Romania itself has around 12,000 caves and there is no limit to what could possibly be down there.
- The man laying explosives has VSSF tattooed on his arm. The acronym translates to Swiss Society of Explosive Engineers.
- Small Name, Big Ego: Briggs is fairly cocky (it's commented that without his arrogance he'd have no personality at all) despite his relatively low-niche in the group and limited qualifications (according to Charlie, he was "table-dancing in a club outside of Calgary" before they hired him), but he does have some Hidden Depths moments and can do his job well enough.
- The Virus: Anyone who is unlucky enough to survive being attacked by the underground flying monsters eventually turns into one of them. It's actually more of a symbiotic virus, intending to help its host adapt to the conditions of the cave, thus surviving, thus allowing the virus to survive.
- Tomboy with a Girly Streak: Charle is a Tank-Top Tomboy who was raised in a dive shop and relishes rock climbing, but also seems to but some effort into styling her hair, wears a bikini nicely and engages in a little girl talk with Katheryn.
- Twist Ending: When the team finally escapes from the Cave, it turns out one of the doctors that entered with them is carrying the parasite with them, and vanishes into the crowd of people.
- Two Girls to a Team: Kathryn and Charlie are the only women on the expedition.
- Unwitting Instigator of Doom: Nicolai, with his decision to explore the cave.
- Vasquez Always Dies: Two girls on the team - trained cave diver and climber Charlie and research scientist Kathryn. Guess which one lives. Though this is semi-justified as Charlie gets killed precisely because she's a climber; she scales a rockwall before everyone else and gets attacked by a creature.
- Walking Swimsuit Scene: Charlie is wearing a bikini at the beginning while working on some equipment on a boat, while waiting on the boat as Briggs, Top and the brothers dive for their latest job.
- Was Once a Man: One of the monsters bears the same tattoo on its hand as one of the cavers previously seen entombed within the cave system at the beginning of the movie. Which bodes poorly for parasite-infected expedition leader Jack.
- When She Smiles: Charlie has a moment of this when laughing and swapping stories with Katheryn, although she's hardly a Perpetual Frowner the rest of the time.