do not play at God (especially when you're doing rounds with him tomorrow)

All you really need to know is that (Dr.) That Weird Guy (™) pinged something on Nadia’s “not this shit again” radar for a few reasons: 1. No-one knew what hospital he’d actually come from, or why, only that he was acting as an interim attending for one of the ER doctors who’d just up and disappeared the month before and hadn’t been heard from again, 2. He supposedly had some experience with battlefield medicine, but no one knew from which battlefield, and, 3. Don’t ask them how they know, but they’re 100% certain they heard him talking to someone on the phone in Classical Latin. Like, fluently. He was having a full conversation with the person until he’d noticed someone else was around and (totally inconspicuously) switched to maybe-French, although it didn’t sound like any dialect Nadia had ever heard.

Or,Nadia El-Amin is just trying to make it through their fourth year of med school without any incidents to rival the night of October 30th, 2017. They don't have time for doctors with unnerving gazes and mysterious pasts, and they definitely don't have time for their outdated ideas of medical practice. They just want this month to be over with already.