Then, we add in the way that Luke lied to Simon in the most obvious way. I mean Simon is Clary’s best friend since practically birth, so it’s a pretty logical assumption that he knows almost everything about her. It’s a pretty logical conclusion to make from someone who didn’t even witnessed Clary telling Simon that she had no other relatives back in Chapter 2. So it was stupid that Luke that told Simon that in the first place. I would also like to mention that Luke had to have known that Simon wouldn’t just stop asking questions until he was personally reassured that Clary was okay.
And then add in the set of bloody manacles on the wall, how Valentine’s minion’s reacted to him, and then the comments he made about not interfering with Valentine’s plans. It just equates that Luke is a shady as fuck, and Clary should never ever trust him.
ETA: It just came to me,, but I suddenly realized (spoiler alert) that Luke is a werewolf with heighten senses. So if he’s as shady as Clare is writing him, then why didn’t he give Clary, Jace, and Simon away? Luke is just so hot and cold, and I don’t understand the reason why.