Alec is neither stunned nor scandalized. He's just trying desperately not to laugh. It's...it's such a ridiculous thing, but Magnus isn't laughing? And Alec doesn't want Magnus to think he laughs at stupid things, but it's so stupid and so funny, and Alec is fairly certain he's going to have an aneurysm trying not to laugh.

And then they reach their stop, and they can get off the train, and Alec thinks that maybe things are looking up, when a skinny, freckled guy slips by them and tries to pickpocket Magnus's wallet.

Alec hardly has time to think before he's acting, grabbing the man by his arm and throwing him.

The man goes flying, arms and legs flailing, and he lands hard on the platform, a crack reverberating through the space. Alec's boot his on his throat before he has a chance to react.