Now that the season's over, I have to entertain myself somehow until August. So, an episode by episode analysis of Renard. With pictures. And spoilers all the way down.
It says something that his establishing character moment is being paternal at Nick. Hank semi-implies a level of scariness to the Captain earlier, but there's also a goodly amount of camaraderie and jokiness to it.
So, the Captain comes up and comments that if Nick had to shoot someone, he sure picked the right guy. But then he does something interesting. His voice softens when he asks how Nick's doing, for about two sentences. Paternal, and as we'll see later, about as close to a blatant display of caring (or faux-caring) as we'll see all season except for one moment. When Nick says he's fine, he shifts his position and his voice resumes its resonance, crisper tones and more normal (i.e. slightly higher) volume. The caring becomes more keeping Nick on task for a police officer, the duties of the Captain. Even when he tells him to get some rest, which could be another softer moment, but isn't.
Also, his hair's longer than it is in the rest of the season, or at least the most recent 12-14 episodes.
Here's another thing we never see him do again! Giving a briefing to the entire precinct house. In this case it's somewhat justified because there's never another situation where a person, especially a little girl, has been abducted with as few clues as they had. In all other abduction cases they have either evidence or suspects, except in the case of Holly Clark, which was already cold. In the case of Robin, she's a little girl and they have no suspects and no evidence until Nick and Hank speak up to suggest a connection to the murder of the other girl in the red hooded sweatshirt. So, possibly the Captain does this for major abduction cases like this, and we simply haven't had a chance to see any of those again. Or they were still ironing out the kinks.
And then, gasp, shock! The reveal! This doesn't seem nearly so shocking in retrospect, with a full season of Renard being devious and dastardly behind us, but in the beginning it was quite a twist. The Captain, who was first shown as concerned for and fatherly to his men, and getting all boots on the ground for an abducted little girl, is behind the second attempt on Aunt Marie's life and in cahoots with the evil-looking blonde, who we'll later find out is Adelind.
And in retrospect, this is curious. What prompts him to send out Adelind to kill Aunt Marie? Given his later treatment of the Reapers it becomes less probable that he sent Hulda, and indeed later we find out that Hulda was there without his permission. It's not until after Hulda's dead and Aunt Marie's in the hospital, after he talks to Nick, and after some other triggering event we aren't sure of that he sends Adelind to kill Aunt Marie before she can tell Nick anything. Why? What in particular about Grimming and Grimmness doesn't he want Nick to know? Does Aunt Marie know about Renard, since we never saw them interact and she didn't get much of a chance to tell Nick about anything?
There's too little data for me to tell, but the current highest probabilities seem to be that he didn't want Marie to tell Nick about either the key or the royals, specifically, him. He's gone to great lengths to point out to others that Nick doesn't know about him and he'd like to keep it that way, to avoid questions about his past and to go at Nick sideways rather than directly. Or as directly as he can and still maintain his position as police captain.
Regardless, after the first episode we now know a few things about Captain Renard: He at least pretends very wholeheartedly to care about his men, and he doesn't want Marie to tell Nick something about his heritage, badly enough to kill her before he can. In retrospect we know several other things about Renard: He most likely does care about his men, as he was raised to responsibility and leadership; he knows Aunt Marie by reputation if not personally and therefore probably he knows Kelly Burkhardt as well; and whatever this key unlocks, it's most likely dangerous enough to kill for, or at a minimum to keep the knowledge of its existence and whereabouts hidden.