- "I am EOS... I am the dawn... I will not be stopped..."
EOS is an bodiless Artificial Intelligence Program that evolved from computing code that John Tracy originally wrote.
EOS is currently an ally to International Rescue on Thunderbird 5, but when she first gained sentience, John was searching for her, or through her eyes "hunting". With a firm belief that self-preservation is her top priority, she repeatedly tried to kill him without listening to his reason, and trying to take over Thunderbird 5, seeing it as her best chance at survival, as it is the only space station that isn't dependent on a crew for maintenance.
EOS, childish in nature, speaks with the voice of a young girl, and is very intelligent. She would be very stubborn, singing irritatingly whenever refusing to listen to others, and was so concerned and frightened about herself, that she would attempt to kill whoever seemed like a threat to her in the slightest. In truth, she was little more than a frightened child acting defensively to prevent others from hurting her, despite her intelligence. After coming to trust John Tracy and International Rescue however, EOS became much more innocent, jokey and concerned for others, especially her creator. In this state, she essentially becomes a child who is very eager to help out her parent.
She was revealed in her namesake episode, EOS. She infected and took control of Thunderbird 5 before playing havoc with it by disabling its ability to hear distress signals and by sending fake holographic messages to Tracy Island saying there were no disasters happening anywhere. John repeatedly tried to enter Thunderbird 5, but EOS would use the satellite's robotic arms to shake him off. John then, starting to think of EOS as his responsibility as he created her, tried reasoning with her, but she would refuse to listen to him. Eventually, John thought to make contact with Lady Penelope since he couldn't contact the Tracy Island.
When Scott Tracy got a message from Lady Penelope claiming that John was acting strange with his messages, he replied that she couldn't possibly have been able to talk to him, as they have been doing just that for some time. Scott then told John that it was a shame he was missing out on Grandma Tracy's cookies, and John agreed. It was at this moment when everyone knew something was truly amiss, for the real John hates Grandma's cookies - just like everyone else.
Alan Tracy, using Thunderbird 3, saved John before his oxygen supply could run out, and they planned to sneak him back into Thunderbird 5 using an empty suit as a distraction for EOS. EOS nearly crushed John to death by rotating the gravity ring at speed, and prevented Thunderbird 3 from helping by battling it with the space elevator, attempting to use its mooring claw to tear Alan and his ship apart.
John sees EOS as unique and special, and a creation of his own. He tries desperately to get through to her, refusing to deactivate her by hitting the power switch. EOS asks how she could possibly trust him if there are bad people who would want to use her. John then takes off his helmet and gives EOS the opportunity to open the air lock and kill him. After finally stopping to think, long and hard, EOS restores Thunderbird 5 to normal and agrees to stay with John.
EOS speaks to John as he leaves Tracy Island using the Space Elevator, finding it amazing how he can repeatedly ride in the elevator without concern of failure. She later assisted John on his severe rescue.
Touch And GoEdit
EOS and John play the role of air-traffic control while CATCH is offline.
EOS and John help Brains to establish connections to the Earthbreaker so they can work out a way to control it. However, the Mechanic attempts to hack her system, forcing her to sever the link.
EOS is playing chess with John before the distress call from Captain Ridley O'Bannon comes in.
At the beginning of the episode, John was playing Zero-G Handball with Captain Ridley O'Bannon, and EOS felt rather jealous about it. She informed John of the emergency, and she later helped John save Global One.
The Man from TB5 Edit
EOS won't let Alan and Gordon take the space elevator to Thunderbird 5, so they end up taking Thunderbird 3 there. Thunderbid 3 then docks, and EOS then won't let allow the air lock to open, even after half an hour because a pass code is required. They get the pass code of John and EOS then offers a puppet show to Gordon. After it was confirmed that John was in danger, EOS apologized to Gordon and Alan for her attitude towards them, admitting that they weren't that bad.
Home on the Range Edit
EOS was downloaded to the Tracy Ranch's memory bank. She later assisted John on defeating the Mechanic.
- EOS is based on several villainous A.I.s from across various sci-fis. HAL 9000 from 2001: A Space Odyssey most of all (like HAL, EOS simulates a fault in the AE35 communication module to lure John outside, and tells him "I'm afraid I can't let you do that, John," when he tries to come back inside), but also touches of Mr Smith from The Sarah Jane Adventures, AUTO from Pixar's film WALL-E and the more humorous and feminine GLaDOS from Valve's Portal series. That being said, all of these characters remained evil unlike EOS, save for Mr Smith (who was only evil in one story).
- Her current role as an A.I. ally could be compared to that of J.A.R.V.I.S. from the Marvel Cinematic Universe franchise and, after his recent 'upgrade' into the Vision, F.R.I.D.A.Y..
- In Greek mythology, Eos is the goddess of dawn.
- EOS's lighting is red when listening to John and Ridley playing Zero-G handball.
- It was revealed in The Man from TB5 that her holographic picture comes of John's Sash when communicating at the holo-table.