Jocelyn Fray (to Alec): According to Luke, you need to stay near the surface. If you go too deep, nothing can bring you back.
Isabelle Lightwood: If you go too deep, by the Angel, Alec, I will kick your a$$ when you get back.
From Shadowhunters – Season 2 Episode 2: ‘A Door Into the Dark’ (2×02)
