Well, it all had to start somewhere, didn't it.
Come back with me to a time around forty years ago - ish - to meet a young man, living in Cheltenham in that garden of England, the Cotswolds, working at GCHQ.
Do you know about that place? It's where the cryptographers and cryptanalysts work for the British Government. Only the best are invited to work there; so even though he's self-deprecating, we know he's very good.
This young man has a very, very good mathematics degree from Cambridge and a PhD ditto, and he loves his work with other very clever people, creating and solving puzzles - and at the end of the day he quite likes going home to his young wife and to play with their new baby.
And for some extra fun, a couple of nights a week, he plays in a little musical ensemble with some colleagues - you know, Bach and Handel and stuff, counterpoint and chamber music (and a bit of jazz when he doesn't think the others are listening).
And he takes things apart and fixes things, and he's interested in all kinds of engineer-y things - a delicious human being, hugely curious, inventive, interested, and completely delighted with life.
He's the youngest one in the ensemble - he calls the others "Cardigans" quietly to himself (lots of the older cryptographers like to wear cardigans over their shirts - very British-engineer), but affectionately, you know, because they're nice blokes, just a bit stuffy. They like him, and he's the best keyboard player they've come across, on organ, piano, harpsichord, anything with a keyboard, really.
He's fairly recognisable, cycling around Cheltenham, with his longish curly brown hair and his big hat, and his long trailing multi-coloured scarf that he has to put in his coat pockets so it doesn't get caught in the spokes. It did once, and the crash was spectacular; his young wife was very upset.
And everyone knows he has many odd things in his many coat pockets, and they all know his great big generous grin. They also know if they stop and talk with him, they'll usually get offered a jelly baby from his endless supply of little paper bags. There's a rumour that he has some kind of special gadget in that coat, too, but nobody's ever actually seen it.
One day the little ensemble - they call themselves the Fiddler's Green Consort, even though they don't exactly work at Fiddler's Green - gets an invitation to come and play in a series of concerts in New York. The Cardigans take a bit of convincing, but by some miracle, the five of them end up in New York to participate in five concerts, and to stay for a whole week.
Our young man is completely delighted to be going to this new place to see and hear all sorts of new things, and he has enough enthusiasm for the entire band, as usual.
They play pretty well, they think, and the audience seems to like them all right, which is nice. Of course, after playing, our young man is full of energy and curiosity, and he wants to go and explore Manhattan - and the Cardigans are content to let him go, while they have a congratulatory (and relieved) nightcap and go to bed.
So he wanders along the streets, and looks at and talks to and smiles at people - sometimes leaving them looking a bit thunderstruck - and somehow he ends up in a bar, talking to people and listening to someone playing the piano, and then listening to and looking at a glorious flame-haired singer belting out show tunes.
And then the guy behind the bar turns out to know the singer, who has the deliciously biblical name Martha; and when she has a break the three of them are talking and having a drink together, where he discovers she's an actor as well as a singer, and even more gorgeous close up.
Our bloke is becoming more fascinated and delighted by the moment, and he ends up taking her home, where they fall joyfully into bed together, and laugh and love all the night through - and it's so wonderful, they do it again the next night, and the next, and the next... and all of a sudden it's almost the end of the week, and he can't even remember whether he's turned up to play at the concerts (he checks with the Cardigans, and they tell him he has).
He's fairly sure he could get addicted to this glorious young woman, if he isn't already. And he thinks she might feel the same. But he's married and he has a young baby, and they depend on him. So he has to tell her about the wife and child, and about leaving at the end of the week - and it's very, very difficult to do. But he's truthful, and he does show her his regret; and she's courageous, and she tries to hide her hurt, and sends him cheerfully on his way.
Aren't they lovely?
And so he goes back to Cheltenham, and never gets to find out about his son, who's already on the way; and Martha, making sure that she doesn't wreck his family, never tells anybody, including her son Richard Alexander, who his father is, although she certainly does know who he is - since she's named her son for him.
Our young man, whose name we now know - he's Dr. Richard Alexander, mathematician, cryptographer, musician - has another child with his wife; his shy, timid English Rose, who has never hurt a fly and who he must care for, over the next forty (ish) years. His children grow up, and then his wife falls ill, and dies, much earlier than he'd expected. The children have lives of their own, and his wife is gone, and all his reasons for getting up in the morning seem to be gone... After some time of grieving and feeling lost, he lifts his head and thinks about what he can do now.
So: after some time of fumbling around and trying things and being unimpressed, he does some research, to see whether he can find Martha-who-he-never-forgot. He knows she's probably got no room in her life for him, but he wants to know she's well and happy; and of course, he wants to see her!
Martha's acting school has been in the theatre news a bit lately - it's even made its way into the Society pages, because of the link with Richard. So it doesn't take him long to find her; and then he decides to travel across the Pond, and at least have lunch with her if he can, and hear her voice and know how she is.
Of course they see each other and it's as if no time has passed; he's older and grey and a good bit heftier and not so spry, but the curls and the grin and the joy are all still there, and she still lights up like a lantern when she sees him - and he discovers that not only was he besotted back then, but that he hasn't actually recovered at all. He tells her how his life has been since they last saw each other, and he beams at her (rendering her legless as before), and asks her how it's been for her.
So then she thinks she'd better tell him about his son. And she does. We don't have to watch that bit, because we might embarrass them. But we can be fairly sure there are plenty of tears of joy.
Castle is sitting in that noxious chair beside Beckett, in something of a game-induced fugue state while she does paperwork, when his phone rings and it's Martha; she says she has someone who'd like to speak to him.
The voice on the phone's a bit older than the one Martha fell in love with, but it's still deep and velvety and English. And without much ado, this voice starts telling Castle the story of his origins, edited a fair bit because our man's still self-deprecating, and with lots more superlatives about Martha.
Isn't it nice how Castle's face is so mobile? You can watch it like a play. That diverting look of wild unholy joy that starts at his feet... see it beginning to take over...
Castle: Where are you?
Doc: I believe I'm at your house.
Castle: I'm on my way.
Castle ends the call, claps Beckett on the shoulder, says "gotta go" without even looking at her and takes off like a two-legged rocket, phone still clutched in his hand.
Takes the stairs because he can't stand still in the elevator, looks at a taxi and starts running, and runs all the way back to his place (still clutching the phone) and bursts in the front door panting like a steam engine, falls figuratively on his father's neck -
and doesn't even see his mother.