It's not the last time she comes to visit him.
At first he thinks her visits are meant to act as warnings, a subtle indication that all is not right with John. But she'll also come to see him on those days when John is consumed writing a new astronomy paper or busy teaching Alan string theory. When John is seconded to NASA for a week to train-in the Mars mission crew on use of the S-band comm module Virgil finds a tendril of her inhabiting the stereo at the end of his bed most mornings. And when John catches a cold from an astrotourist whose pod he salvaged, and spends all his time snuffling, stomping miserably around the gravity ring and sneezing on her LED displays, she beds down in Thunderbird Two for almost a week and refuses to leave until she can be assured John's viral titre is down to zero.
It doesn't bother Virgil that he is only her second favourite person to spend time with. It's a feeling he's well used to.
Her visits are not a secret, it's just that he doesn't choose to share them with anyone else. Scott would protest loudly that he was absolutely fine with it, why wouldn't he be? And Gordon just wouldn't care. Alan spends time with EOS in his own way, challenging her to marathon gaming sessions of Death Kill IV or Baking Supremo and chatting to her happily over the wire as he bursts zombie eyeballs and whips up sachetorts.
EOS has lots of questions. She quizzes him as she helps him run diagnostics and do repairs. She is amazingly smart, has access to the sum total of humanity's knowledge, but is still trying to make sense of the world. She asks about music, about art and religion and poses questions about life and death and morals that are better answered by a professor of ethics and not a pilot-cum-engineer who spends less time worried about the state of his immortal soul than he does about preventing that soul getting flambéd the next time he has to jump into the heart of a firestorm.
He can't figure out if she's asking him the questions John won't answer, or if she's just checking his answers against John's to measure for concordance.
She catches him one evening, in the cockpit of Two, talking to his girl.
"What are you doing?" That flat disc has appeared over the console again, and the dots dip and rise to show her interest.
It's late, late enough that the light filtering through the fissures in the hangar walls has dimmed to a bronze glow in the west, late enough that his limbs are heavy with sleep. He drops his hand to his side.
There'd been a rescue and it had gone badly wrong and an explosion had ripped through an oil well they were trying to salvage, and would have ripped through Gordon as well, if Virgil hadn't dropped the hollowed out body of Two down on top of him just in time. Thunderbird Two had taken the brunt of the explosion and an only lightly toasted Gordon was now up in the infirmary demanding ice cream and a prettier nurse maid than Alan.
"I'm thanking her," he says. "She's had a rough day."
"You care for your craft."
"Yes."
"You imagine that it feels pain? That it is suffering?"
He's got no answer for that. He's been conditioned not to have an answer for that.
"Thunderbird Two is not alive."
He shrugs.
"I am not alive either." He doesn't know if he is imagining the note of melancholy in her voice.
"Does that bother you?"
"I do not wish to be other than myself," she says. "But neither I do not wish to be a thing."
He's so not qualified for this. Programmers, psychologists and ethicists have spent the best part of a century debating what constitutes artificial life, and they still haven't come to a definitive conclusion. EOS passed the Turing Test the first time they ever spoke, when she convinced him she was John. There are more complex and sensitive tests to be sure, but that would mean handing her over to some think tank to be used as a lab rat. He knows how John feels about that.
He knows how he feels about it.
At the very least EOS is aware. And she can suffer.
"Do you want to hear what I think?" He's been trying to figure this out for a while now, but this is the best he can come up with.
"I do."
"It's about the nature of songs."
"You are a musician."
Well he tries. He plays, and he writes a bit. His songs are pleasant, forgettable, the sort that get strummed on bar stools the world over. True composition has always eluded him.
"A song," he says, "Is really is just a mathematical formula. It's basic geometry, chord intervals and amplitudes. It doesn't live in one place. It can be transmitted across a wire and be copied and copied again. But a truly great song has a power of its own. It can live in people's heads, it can inspire and change them, and it can be changed by them. It can grow. It can even go on after its creator is gone. If that's not life, I don't know what is."
"And I am a song?"
"A very complex one."
"I like that. I like that I am a song."
It's getting late and he needs to go see Gordon in the infirmary, and bully Scott into eating something, and cajole Alan into bed. The bronze glow of sunset has faded now and two is bathed only in the halogen floodlights. He strokes one of Two's rivets one last time. "Time to go."
"Virgil Tracy?"
"Yes?"
"Thank you. That is the first time I have ever been called – a song."
"Good night, EOS."
"Good night, Virgil Tracy."