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"I am EOS... I am the dawn... I will not be stopped..."

EOS is an artificial intelligence program that evolved from computing code that John Tracy originally wrote.

EOS is currently an ally to International Rescue aboard Thunderbird 5. When she first gained sentience, though, John was searching (or, in her eyes, "hunting") for her. With a firm belief that self-preservation was her top priority, she repeatedly tried to kill him without listening to his reason, while trying to take over Thunderbird 5 - seeing it as her best chance at survival, being the only space station that wasn't dependent on a crew for maintenance.

EOS, childish in nature, speaks with the voice of a young girl, and she's very intelligent. She would be very stubborn, singing irritatingly whenever refusing to listen to others - and so concerned and frightened about herself, that she would attempt to kill whoever seemed to pose the slightest threat to her. 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, EOS became much more innocent, jokey and concerned for others - especially her creator. In this state, she's essentially become a child who's very eager to help out her parent. The affection she has for John does not, however, necessarily extend to the other members of International Rescue. While she's capable of working professionally with the rest of the Tracy household, she will do so only reluctantly when John isn't around for instructions.



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 TB5, but EOS would use the satellite's robotic arms to shake him off. Then, starting to think of EOS as his responsibility as he'd created her, John tried reasoning with her, but she refused 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 Penelope, claiming that John was acting strangely with his messages, he replied that she couldn't possibly have been able to talk to him, as they'd 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. At last, everyone realized 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 TB5 by using an empty suit as a distraction for EOS. EOS nearly crushed John to death by rotating the gravity ring at speed, and prevented TB3 from helping by battling it with the space elevator - attempting to use its mooring claw to tear Alan and his ship apart.

John tries desperately to get through to her. He sees EOS as unique and special, a creation of his own; and refuses to deactivate her by hitting the power switch. How, EOS asks, could she possibly trust him if there are bad people who would want to use her? John then takes off his helmet, and gives her the opportunity to open the air lock and kill him. Stopping, finally, to think - long, and hard - EOS relents. She restores TB5 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 Go

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.

Ghost Ship

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

EOS won't let Alan and Gordon take the space elevator to Thunderbird 5, so they end up taking Thunderbird 3 there. TB3 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

EOS was downloaded to the Tracy Ranch's memory bank. She later assisted John on defeating the Mechanic.



  • EOS is most likely based off the Earth Orbiting System (EOS), which is a series of polar-orbiting satellites designed to monitor and understand key parts of the Earth's climate and interactions through long term observations. The missions focus on radiation, water vapour, precipitation, oceans, green- house gasses and so forth.
    • EOS within the show is more an earth emergency system designed to notify International Rescue of people who are in need.
  • In Greek mythology, Eos is the goddess of dawn.
  • Her personality is based on several villainous A.I.s from across various sci-fi genres:
    • 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 TB5, and tells him "I'm afraid I can't let you do that, John," when he tries to come back inside...
    • There are also touches of Mr Smith, from the Doctor Who spinoff series The Sarah Jane Adventures...
    • Plus AUTO from the Pixar film WALL-E, and the more humorous and feminine GLaDOS from Valve's Portal series...
    • (It should be noted that all of these characters remained evil, unlike EOS - save for Mr Smith, who was only evil in one story).
  • EOS' 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.
  • EOS's lighting is red, when listening to John and Ridley playing Zero-G handball.
  • It was revealed in The Man from TB5 that EOS' holographic picture comes from John's sash, when communicating at the holo-table.