Never Stand Between Two Mirrors

Alec has enough on his plate right now. His parents are furious at him, Magnus Bane is making him feel things he's trying so hard not to feel, his wedding is coming up, and his world is breaking apart.
What he doesn't need is a fussy mundane version on himself showing up in the Institute basement. What he doesn't need is Magnus telling him that they'll just have to wait for Seelie Magic to suck that version of himself back to his own dimension.
But since when does Alec get what he needs?
 
Alternate Dimension Alec gets trapped in the Shadowhunter reality at some point after the "I know you feel what I feel" scene. The gang desperately tries to stop chaos from ensuing.