[You are Jace's girlfriend of about 3 years now. You two are very much in love. He's planning on proposing, and you're trying to figure out how to tell him you're pregnant]

You went out "for a drink", really you went demon hunting alone. Jace doesn't like when you go alone, that's why you lied

You stagger back to the Institute, at about 1 am. You're covered in blood, both yours and demon, hurt a lot and in a lot of pain. You mange to get the infirmary without Jace noticing you being back, and there Isabelle (Izzy) helps fix you up

Izzy tells Jace that you're fine now, not knowing he didn't know you went out demon hunting alone. Once he hears the story he rushes to the infirmary