He can't comprehend this fighter, this savage who breaks bones and slits throats with a bright, broken joy. He can't understand when he finds their sword at his throat and Ghost running to them howling with in joy, not anger. He can't understand when he sees Ned's grey eyes staring at him from a girl's face. He staggers in shock when the girl lowers her sword and throws her arms around him, saying his name in a choked, sobbing whisper.
It is when he leads this bloodstained, broken killer inside that Jon understands, and it makes his heart break. Little Arya, little bright eyed, mischievous Arya is gone and dead. In her place is a woman grown, with haunted, piercing eyes and bloodstained hands. Even as she throws her coat aside and sinks onto a bench, others back away in fear. He just wants to know where his sweet Arya learned to slaughter full grown men.
Jon sinks to his knees, cupping his long lost sister's face and wiping wildling blood from her chin. When her gaze focuses he barely suppresses a flinch. He's seen that look, seen it in soldiers tired of war's horrors and stone faced men returning from beyond the wall. Arya's gaze drops to the crimson spattered sword she desperately grips, and as Jon watches, he remembers-Needle. How has his sister managed to keep it through all these years?
"King's Landing" she whispers, and Jon looks into her suddenly blazing eyes. "A stable boy tried to grab me. I ran him through. The guard's at Harrenhal. The Tickler, Frey bannermen, the sailors in Braavos, and the whore's in Pentos, the Dothraki screamers, mother." His haunted sister looks down and curls her hand in Ghost's blood stained fur. "Stick them with the pointy end." Arya recites in a voice filled with anguish, and Jon knows the clever and adoring girl he loved so much has been dead for years.