Thorn.
Al didn't understand many things now. Things like why so many people seemed to know him, or why Winry was suddenly so old. He didn't understand why his brother was gone, or why the strange boy with the wild hair and the purple eyes came to visit him late at night some times. It was all part of That Secret, which no one ever told him about, and which made Winry's eyes watery and sad.
Above it all, he didn't understand why, the day he fell off the stairs into the rosebushes Winry had planted after he'd arrived home - from somewhere he didn't remember, he didn't remember leaving - Winry had laughed.
He'd laid there, crying as the thorns viciously bit onto his skin, bleeding profusely out of a thousand and one little wounds that were too small to leave scars, and Winry had come. Her eyes had filled with tears at the sight of blood pouring out of his skin and her arms had found their way around him, cradling him against her almost desperately.
And then she'd laughed.
Alphonse cried harder at that, not understanding or knowing why. He couldn't know how deeply it affected his childhood friend to see him bleed, see him feel. He didn't remember the emptiness of a cage made of steel. He didn't remember the loneliness or the delicate, loving trace of blood that kept his soul together for so long.
Thus he didn't understand how his pain, his agony - increased tenfold by his childish panic and his stung pride - could make Winry cry tears of joy mingled with saddened laughter.
His body was torn by the wounds, it would heal and be fine again, and in a few years, it would only be a sour memory to share late at night remembering old days; but for Winry, for the one who had stayed back and waited, it was a testament to all the loss, the tragedies...
It meant Ed hadn't left them all in vain.