Castiel is five years old on the day he starts school, the number he wrote on his hand is 4122, but he doesn’t know that yet.
On the day he learns his 1 to 10, the number on his hand is 4119 and his teacher asks him who taught him such a big number, Castiel tells her that it was nobody and his teacher looks confused.
He’s eight when he asks Gabriel what the numbers mean, and Gabriel just shrugs and says,
“You’re the one writing them, Cassie, you should know.”
But that’s not fair because Castiel doesn’t know and Gabriel is supposed to know everything.
He’s ten when he realises that his mother no longer keeps pens in the house. On the day he makes this realisation, the number on his hand in purple felt tip says 2421 . He still doesn’t know what it means, but it gets one less each day and Castiel knows that he’s counting down to something.
He’s thirteen when he tries to stop, his mother doesn’t keep pens in the house any more and he knows he’s worrying her. He refuses to write the number on his hand during the day, ignoring the nagging compulsion for all of his waking hours, but he wakes up halfway through the night with a pen clutched in his right hand and that number, one less each day. He goes to the bathroom and scrubs till his hand is red and the tears pricking at the backs of his eyes are no longer a going concern.
He’s fourteen when he stops trying, the hours spent rubbing at his hand in the early morning taking their toll until Castiel decides he simply doesn’t care. It’s stupid to think he’s counting down to anything. He still hides his hand from his mother though, writing the number in inconspicuous places as small as possible, he never wanted to upset her.
He’s seventeen when he finally reaches 0, and he prays it’s over. The pen today was bright green, found in the hallway on his walk to class. He’s just taken his seat when someone he doesn’t recognise walks in. Castiel sees the stranger’s hand and his world stops, there in bright blue ink on the back of the other boy’s hand is a huge 0, unlike Castiel, the boy -Dean, his teacher just called him- is completely unapologetic about the number and Castiel thinks Dean is what he needs.
From the moment he walked in with that huge 0 on the back of his hand in bright blue ink, Castiel knows that Dean Winchester is what he’s been counting down to.