In the year 2063, Global Warming has caused most of the world's landmass to disappear. Only two continents remain, locked in a state of cold war enforced by the military outpost Sentinel, a tiny sea fort battered by regular storms and falling apart due to rust and metal fatigue.
Sentinel is manned by a skeleton crew of only four soldiers; their by-the-book commander Sgt. Hendrichs (Thomas Kretschmann); Cpl. Cassidy (Kate Bosworth) who serves as his Number Two; Baines (Martin McCann), and 'Sully' Sullivan (Lucien Laviscount) who is Cassidy's lover. Their two-year contract ended three months ago, but the relief crew never arrived. Trapped in the middle of a vast and hostile ocean the crew are starting to wonder: Has war broken out again? Is there anyone still alive back home? Does the enemy even exist? Or has the enemy been among them all along?
Not to be confused with the 2007 post-apocalyptic film The Last Sentinel.
This movie has the following tropes:
- Ambiguous Situation: Did Cassidy murder Baines, or did he just go insane and drown himself like she said?
- Artistic License – Military: Sentinel is chronically undermanned for a military base holding a WMD deemed crucial for the defence of the country (presumably because it's a suicide post if the device ever has to be used) with no leeway for crew falling sick or accidents. Instead of a unit of marines for the sole purpose of defence, they have a single pistol and artillery piece. While they take precautions against unknown boats approaching, there's no sonar against submarines which might travel beneath the bad weather and carry frogmen to attack Sentinel in between the storm surges. The fact that there's a spy on board implies their enemy has the means to infiltrate Southland at the very least.
- Bad Vibrations: Things start to rattle and break on the ill-maintained sea fort as the storm surge approaches.
- Bait-and-Switch: Every male character is presented as a potentially unstable threat to the others at one point or another. It's Cassidy, presented as the most reliable, who turns out to be the most dangerous, as she's an enemy spy who's already murdered their relief crew.
- BFG: Sentinel's only defence is an artillery piece mounted on the roof.
- Break His Heart to Save Him: Cassidy breaks the impasse with their commander by agreeing to stay on the Sentinel while Sully and Baines take the Aurora to get help. Having fallen in love with Cassidy, Sully then refuses to leave, so she tells him he was just a convenient fling for her. She apologises afterwards when they're all forced to stay.
- Chekhov's Gun:
- Sully asks Baines if he can shut down Martha in case Hendrichs goes mad and tries to set it off. Baines says he can do it given time, but is reluctant to commit an act of sabotage. But after Baines nearly sets off the bomb himself, he carries out Sully's request, a fact that Sully doesn't realise until he tries to set off the bomb.
- Part of the railing where Scully boards the Aurora from his dinghy has come loose. It had been removed by the crew to allow their murderer, who was also in the dinghy, to come on board.
- Doomsday Device: Martha is a twenty megaton bomb that, if detonated, would create a tsunami big enough to wipe out Northland—and likely their own country as well, Baines suspects, making it a literal World-Wrecking Wave.
- Decontamination Chamber: A mundane version; radiation emitted from Martha means the crew have to take regular iodine baths and then get hosed down afterwards. The seals on the bomb are decaying as well, meaning the radiation levels are increasing, but they're running out of iodine until they find more on the derelict relief boat.
- Dead Man's Switch: A pressure switch on the arming panel is held down by the operator while the bomb activation code is entered.
- Ear Ache: When Baines refuses to fire upon the Aurora, Sgt. Hendrichs shoots his ear off.
- Earth That Was
- Baines salvages toys from the ocean for a child he hasn't even seen yet, and talks about how the Borg chair he's futilely trying to restore is from Estonia, a country that no longer exists, requiring fabric panels that are no longer manufactured.
- Sully gives Cassidy a gift he found on the Aurora; a silver incense globe engraved with a map of the world as it used to be. Neither of them can work out what it is.
- Face-Revealing Turn: The person dressed in a rain cape rowing out to the Aurora appears to be Baines until she turns and guns down the crew, revealing herself as Cassidy.
- Freeze-Frame Bonus: Sully has Don't shoot it's me written on his helmet (shown right before Hendrichs orders him to fire on the Aurora).
- Giant Wall of Watery Doom: Sentinel is hit by a massive wall of water almost as high as the sea fort, which manages to knock it onto a slight angle.
- Ghost Ship: The Aurora is found drifting in the ocean with its crew missing, but stocked full of supplies and the kit of four marines. It's obviously the ship that was supposed to bring their relief three months ago, but what happened to them?
- Gone Mad From The Isolation: Four marines isolated on a tiny sea fort in a vast ocean, three months after they should have gone home. The thought that everyone back home may have been nuked, or that their enemy never existed in the first place, doesn't help matters.
- Green Aesop: Find balance; stop fighting over resources and start working together.
- Help, I'm Stuck!: In the opening storm scene, Baines nearly drowns when he gets his hand stuck.
- Here There Be Dragons: A world map shows only two landmasses. Southland, where the protagonists are from, is marked Home Sweet Home. Northland, where the enemy is supposed to be, is marked Here Be Dragons. It's not entirely facetious as no-one's made contact with Northland for forty years, and some speculate they've all been wiped out and the government's just keeping up the pretense as a Genghis Gambit.
- Hope Spot
- Cassidy convinces Hendrichs to allow two men to return home in the Aurora while the other two stay to guard the Sentinel. That night Hendrichs sets the Aurora adrift and forces the crew at gunpoint to sink it with the cannon.
- Baines appears to recover after trying to set off Martha, so Cassidy allows him to go with her on a scavenging trip. Sully takes the opportunity to look through the confidential files and finds he's dangerously unstable. Then he only sees one person in the dinghy rowing back to the Sentinel...
- Never Suicide: Sully goes to release Hendrichs, only to find he's apparently jumped from the window of his cell into the ocean. Only Sully hauls his body up in the net with an obvious head wound. Then Cassidy returns claiming Baines went mad and tried to walk off across the field of debris.
- No Blood for Phlebotinum: Once the environment was screwed up and the world started flooding, humanity made things worse by fighting over what land and resources remained. Cassidy tells Sully that the attempt to seize the Sentinel, and Southland after that, is a desperation gambit as her continent is sinking under the sea.
- Once More, with Clarity: When Scully realises the truth, we get a scene showing what happened to the Aurora. Cassidy was on duty that night, so she paddled out in the dingy with the homing beacon to lead their relief boat away from the Sentinel, then shot the crew as they gathered at the rail to haul her on board.
- Poor Communication Kills
- When boarding the Ghost Ship, Sully turns off his radio because he thinks the static will give him away. Because Hendrichs can't make radio contact, he arms Martha in case the ship is full of enemy commandoes.
- Hendrichs plots the GPS position readings recorded on the Aurora's e-log. From this he realised that someone deliberately lured the relief ship away from Sentinel as it approached. Realising there has to be a Mole on Sentinel, he has the Aurora blown up so no-one can leave. However he only reveals what he's found to Sully after he's been locked up by the others as a lunatic, so Sully thinks he's crazy or it's just a ruse to get himself out of his cell.
- Precious Photo: The photo Cassidy keeps looking at is assumed to be her family back home, including a husband she is cheating on with Sully. But Cassidy tells him that the person who looks like her is actually her mother; it's a photo of her parents and brother who were killed during the war. It's also a Cover Identity Anomaly when Sully realises it's raining in the photo, when all he remembers from his childhood is the constant heat from the lack of rain in Southland. That's because Cassidy grew up in Northland.
- Product Placement: A more subtle version than most; the movie is an Estonian production and the chair Baines is trying to restore is from Borg, a company based in Estonia.
- The Radio Dies First: Sentinel is under Radio Silence with a satellite passing overhead to relay messages in an emergency. Sully disobeys orders and sends out a report on the Aurora, only to get the same message sent back to them because it hasn't been downloaded. This raises the question of how long their communications have been down, and whether there's anyone alive back home to receive their message.
- "Ray of Hope" Ending: War is likely to break out again, but Sully and Cassidy agree to defend the Sentinel against whichever side comes to claim Martha. And birds are supposed to have gone extinct because their migrations were ended with the sinking of the landmasses, yet swallows are seen at the end of the movie.
- Reassigned to Antarctica: There's indications that despite all the propaganda, and high pay offered to anyone who volunteers to spend two years on Sentinel, it's actually this trope. Sully is supposedly Only in It for the Money, but he's actually serving there to avoid an even longer prison sentence. Baines is psychologically unsuited for the role, but is sent because he's an excellent engineer. Sgt. Hendrichs lost his entire unit in a Noodle Incident, something he blames himself for and apparently his superiors did as well.
- Scavenger World: The crew supplement their supplies by lowering a net into the ocean and catching the fish that are driven into it by the storm, as well as taking the dinghy out to the vast fields of floating debris. Both are risky operations because you have to get back to the Sentinel before the storm hits, and there's not enough fuel for the outboard engine, so the dinghy has to be rowed.
- Spreading Disaster Map Graphic: In the title sequence an outline drawing of the continents gradually changes to the two remaining in a Flooded Future World.
- Sword of Damocles: Martha is a deterrent against a Northland invasion; an atomic bomb that will unleash a tsunami that will overwhelm the continent if Southland is attacked.
- Two-Keyed Lock: Though not a very effective one. Martha requires two keys to activate it, but they can be inserted by one man who also holds down a Dead Man's Switch, preventing anyone from stopping him. When Hendrichs refuses to return Cassidy's key, it doesn't help ease tensions among the others.
- Walking Shirtless Scene: Lucien Laviscount has the best abs, so he does several of these.
- Weather of War: Sentinel was built where the relief boat had just enough time between storms to get there and back, but far enough from Northland that the enemy doesn't have time to reach the sea fort before running into a storm. However it's pointed out that the weather has changed over forty years, so this might not still be the case.
- Where's the Kaboom?: Baines goes mad and tries to set off the device, only to forget the last digit of the activation code. Then Sully tries to detonate it after realising Cassidy is a Northland agent, because her country is planning to invade. Cue Distant Reaction Shot...and nothing happens because Baines has deactivated Martha. In the end Cassidy and Sully call a truce and agree to make sure no-one else sets it off.
