‘Last Sentinel’ (2023) Ending, Explained: Who Is The Real Traitor Amongst The Crew?

Last Sentinel 2023 is a slow and tedious movie leaning on the same old trope of “you lose your mind after too much loneliness,” but later adds a random twist to the tale that comes so late in the film that the whole premise of climate change and war is lost in a second. Visually, certain scenes are mesmerizing, especially when there are just the roaring waves and the ocean for miles and miles in the distance. Last Sentinel takes place in a dystopian future that is imminent, but something about it is too old-fashioned to get the clocks turning. Let’s work out the ending of Last Sentinel


Spoilers Ahead

Plot Synopsis: What Happens In ‘Last Sentinel’?

Four soldiers are stranded on a military base in the middle of the sea in the year 2063. The crew waits for a relief support team that was meant to arrive over three months before. The world as we know it has been destroyed by the climate crisis and rising sea levels. Only two continents remain, and they are at war. The soldiers spend their entire time awaiting the enemy or relief to arrive. Every day, a message is sent through Morse code over a radio device. Soon we learn that the Sergeant is very uptight, and the soldiers under him aren’t very happy. At the beginning of the movie, a storm is coming, and Sully and Cassidy, the corporal and private, are trying to catch fish in a net. They’re very happy to see the fish, but the storm comes early, and before they can save the fish, the net falls back into the ocean. Sully stays back to save it, but Cassie heads up to safety. He hooks the net, but at the last moment, the fish are lost.


The next day, Private Baines, the engineer of the crew, is terribly angry about the fish being lost. The storms are a recurring occurrence, and it looks like the next one will come sooner than the previous one. Sully is the most fun of the lot; he cooks the food and manages communications. As we know, the Sergeant is on edge at all times. Baines is an excellent engineer but needs things to happen right, or he’s impatient. Cassidy is the calm one of the group and keeps them all together. There is a bomb in the base that can be detonated at any time by the Sergeant, but one key is with him and one with Cassidy. Soon, a small ship appears on the radar, and Sully is the happiest, imagining it is their relief. According to protocol, the team needs to aim their artillery at any approaching ship if they do not communicate.

Sully is sent to check the ship while the rest wait. Sully finds it empty and sees some food and supplies. He sits down to eat some chocolates, and at that time, the Sergeant has already set up the bomb, which is code-named “Martha,” to direct towards the ship. Sully barely replied in time, saying the ship was empty and “Martha” was turned off. Sully and Cassidy are in a relationship, and while Baines and the Seargent take a look at the ship, they have some alone time (a way to pad out the film’s runtime). The captain says they need to break down the ship and take all her parts before the next storm hits, but Baines and Sully have decided it is time to leave their posts and head home. Suddenly, they’re united against the Seargent. Cassidy is always looking at a photo of what looks like her family—a couple and their two kids in the rain with umbrellas. The Sergeant will not allow the crew to leave, so they all begin to fight. Sully and Baines have made up their minds, but Cassidy is the one who can change the mind of the Sergeant.


In some time, he says two people will go, and two will stay back. Sully is mad at the prospects because Cassidy has volunteered to stay. He tells her he will not leave without her, so either she goes instead of him, or they both stay. She tells him she doesn’t love him and tells him to go. Sully packs and the Sergeant answers his question about the other continent. He says they are the same as their own people, eating, drinking, excreting, and living just like them; the only difference is that the people of the other continent are out to get them. Sully understands that the Sergeant is a good man, but he’s too busy worrying about protocol. Just when things might be looking up, they quickly take a dark turn. An alarm is blaring, and a ship is approaching the base.

The Sergeant asks Baines to ready the artillery to fire at it, but just as they’re about to, Sully and Cassidy realize it is their found ship that has floated away. Baines disobeys the Sergeant, and he shoots at his ear. Sully is frightened by the ordeal and fires the artillery instead, destroying the ship. Baines is completely disoriented after being shot in the ear, and before the Sergeant can shoot him, Cassidy hits the Sergeant on the head. They put him in a room and lock it, leaving Baines wandering around, trying to break him open. Baines wants to kill the man, but Sully stops him from doing anything harsh. Things get worse with Baine, who begins to drink a lot and stop engineering, and the Sergeant tells Sully that he needs to bring him out because that ship might be an enemy ship. It had arrived three months before and had changed course, which is what had made the Sergeant concerned, and it was one of their comrades who might have killed the crew. Sully doesn’t believe him and leaves.


‘Last Sentinel’ Ending Explained: Whose Ship Was It In Reality, And What Happens To The Base?

Baines steals the keys from Cassidy after violently putting pressure on her in his drunken state. By the time Sully arrives, he is putting in the pin to launch Martha. Sully reminds him of his wife, Liz, and convinces Baines that things will be okay soon. It works, but Baines has already forgotten the last digit of the pin (did we need a sudden burst of dry humor in the last act? We don’t think so.) Baines becomes well and normal after that conversation and fixes up everything at the base. In the meantime, Cassidy shows Sully the picture of her family, and Sully had asked her earlier if she didn’t want to see them. Now she tells him it was her parents and her brother who were killed by the enemy raid when she was sent away for school. Sully and Cassidy also learn from Baines that the Sergeant jumped out of the window to his death.

The next day, the storm is arriving (2 days early), and Cassidy says she will go salvage some debris for materials they need. Baines tells Sully that he is going with Cassidy, and he thanks him for showing him support and reminding him of his wife, who was pregnant when he left home. He doesn’t even know if it’s a boy or a girl, so he hugs Sully in excitement to go back and see her and the child someday soon. Before leaving, he tells Sully that he “did” something important for the “cats, swallows, and horses.” When they first drank together, Sully said, “If Martha destroys the world, what will happen to the dogs, horses, and swallows? Sully doesn’t pay much heed to it but understands it later. When Cassidy and Baines leave, Sully tries to get the fish. Along with the fish, he also pulls up Seargent’s body and sees a bullet wound in his head.

Realizing that it is either Baines or Cassidy who is the traitor amongst them, Sully goes to look for all the clues in their personal information. Soon he realizes the Sergeant was telling the truth about the ship, and we see the present scene and what happened three months ago simultaneously. A hooded person headed to the ship that night and killed all the crew members. It was, in fact, Cassidy who did it, and when she returns from the debris site alone, Sully’s suspicions are proven right. He pretends as if he believes her when she says that Baines chose to go across the debris, but the next morning she wakes up alone in bed. Sully has prepared Martha, and by the time Cassidy arrives, he has put in the code and is awaiting the explosion. He tells her that he should’ve known before because it never rained on their continent. Cassidy was actually a spy from the other side, and her mission was to stop Martha from being set off. They are the only ones who have Martha. Now, because of her, the whole world will be destroyed. But Baines’ last move was to save the swallows, cats, and horses, so the thing he had done before they went out at sea was disarmed Martha for good. Now, Sully and Cassidy are each continent’s last surviving soldiers at the base. They decide that they will fight the enemy, whichever side they come from, in order to save the swallows. The film ends with the sound and appearance of some swallows far away from the military base.

Final Thoughts

The movie has a great idea to be a psych-thriller-dystopia like “Triangle” and has elements of great films, but the storytelling is dry and unengaging, making one lose interest even if it is about the end of the world. The message is obviously clear: the climate crisis is here and now, and the future looks bleak and war-ridden, but it’s all lost in translation.


Ruchika Bhat
Ruchika Bhat
Ruchika, or "Ru," is a fashion designer and stylist by day and a serial binge-watcher by night. She dabbles in writing when she has the chance and loves to entertain herself with reading, K-pop dancing, and the occasional hangout with friends.

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