The Last Sentinel Ending Explained- Who Was The Traitor And What Did The Horses, Cats, and Swallows Message Mean?

Tanel Toom’s The Last Sentinel, written by Malachi Smyth and currently streaming on Amazon Prime and Tubi, is a dystopian thriller about the world’s end and the mistakes humans keep making. We can’t help ourselves. Humans mistrust and fight. Films like Annihilation and Arrival argue from different view points whether humans are worth saving. We covet what others have and steal and kill to make it happen. Until we stop viewing others as enemies, it will never change, and the world is doomed. In the end, though, there is one final beacon of hope. Here is everything you need to know about the ending of The Last Sentinel: who was the traitor, and what Baines’ message meant.

In 2063, climate change has progressed unchecked, and sea levels have risen so much only two small continents exist. The rest of the world is underwater. The two land masses are constantly at war with one another, and everyone on the planet fights for survival and resources. It’s a bleak place of extreme conditions and temperatures. Standing in defense of the continent without rain is the last sentinel with a weapon affectionately called Martha.

The four-person crew works and waits tirelessly for their replacements. They have been on the sentinel for two years, and replacements were supposed to come three months ago. Tensions are high. When a ship called the Aurora arrives empty, the crew is torn on what to do. Two want to repair the ship and return home. Another wants to remain on the sentinel and man their posts. Corporal Cassidy is left in the middle, hoping for a resolution.

Day after day, they send and receive messages to their continent. After the Aurora shows up empty, Sully sends a message detailing the mysterious ship and asking what to do. The next day, instead of getting an answer, their message looped back around to them. At this point, Sully thinks the worst and assumes all our war has ensued between the continents. The soldiers break down as mutiny and panic break out among the crew. Heinrichs and Cassidy will stay on board, and Sully and Baines will take the ship back home, but when the Aurora is blown up during a crew fight, Cassidy knocks Heinrichs out, and the soldiers retreat to their quarters.

Heinrichs explains to Sully that the ship had already been at the base three months ago and returned. He is convinced Cassidy or Baines sabotaged the mission and is working for the other side. Ironically, he was right. He was rigid and dangerous, but he wasn’t wrong about there being a spy in their midst. His fear made him a good soldier, but he was unable to adapt to the situation.

Baines gets drunk after the ship is blown up and attacks Cassidy. It looks like he is the traitor, but he is just despondent. Being isolated from his family and with no hope of rescue, he loses it and decides to fire the weapon. They manage to stop him, but then they realize that Heinrichs is missing from his room. Later, Sully found Heinrichs’ body with a bullet hole in his head, and Cassidy tells him Baines attacked her and was lost at sea. Just before all of this, he reads Heinrichs’ file and knows he wouldn’t have killed himself. Now he knows Cassidy was the one who killed the relief crew and most of the sentinel’s current crew.

The ending of The Last Sentinel

After realizing Sully had been sleeping with the enemy all this time, he sneaks out of bed while Cassidy is sleeping and prepares to launch the bomb at her continent. They have a tense conversation, and he tells her he knows she killed everyone. Cassidy explains that she was taught very early that it was her group or theirs, and there could be no compromise. Just before Sully triggers the bomb, a message is received. Baines coded a message into the bomb sequence to remind Sully what was at stake.

The message was about the vulnerability of everything else and that we shouldn’t destroy the world because nature didn’t deserve it. Upon seeing the message, Sully stops the sequence, and we next see Sully and Cassidy in the mess hall discussing the next steps. The two decide they will keep Martha out of both continent’s hands at all costs. The world and everything in it is more important than their warring factions. Finally, equilibrium has been achieved, and there is hope for the future.

Who was the traitor?

Cassidy was a spy for the other side. She was from the continent with rain, while everyone else on board the sentinel was from the continent without rain. Sully realizes this when he remembers that Cassidy’s picture of her family showed them in the rain. This meant she had to have been born on the rainy continent.

Baines says his wife thinks the enemy is long gone, but their government uses the threat of an enemy to control everyone. Baines and Sully also discuss that Earth is at a tipping point, and it wouldn’t take much to annihilate it. If Martha is deployed, everything will die, including all the innocent horses, cats, and swallows. This becomes very important at the end of the film.

Cassidy is a traitor, but she finds purpose in life at the end of The Last Sentinel. There has been no contact with the outside world, and they feared the worst. It is possible no one is left at all. There are still animals, fish, and birds though. Those animals are innocent; perhaps people don’t matter as much as life does.

Throughout The Last Sentinel, we are presented with constant paranoia. All four soldiers appear to be traitors at one time or another. Baines could be losing his mind after too much time at sea. Heinrichs has all the markings of a Hunt For Red October closemindedness that could get them all killed. Sully rebels against protocol and is paying off a criminal sentence by serving on the sentinel. Although they are different, their emotions are the same. They all think they are saving their people from death.

When Cassidy shows her family picture to Sully, she shares a story. The umbrella story is indicative of the conflict between the two continents. Cassidy was grumpy in the picture she showed Sully because she wanted the bigger umbrella that her brother had. Both continents want the resources for themselves instead of working together or being grateful they had anything. It is not until the end of the film that Cassidy realizes protecting everyone from the storm is more important than having the biggest umbrella.

The Last Sentinel is about loyalties and betrayals. At its heart, it is about who we side with and who we are willing to sacrifice for our survival. After everything they had been through and after learning they were on opposite sides, Sully and Cassidy decided to work together to save the world. Baines’s final message got through to them. Everything is not about us, and we need to change to safeguard the world and those who are innocent. They decide to keep the weapon away from both continents. The station is balanced once again, just as there is finally peace and real hope for the future. The birds flying and chirping at the end signifies change is possible, and hope is not lost.