Pushed forward by curiosity, Inanna moved closer. There, half-hidden by the bushes and flowers, she glimpsed blue and white. It took a while for her vision to register itself in her mind. The blue was that of the tunic of House Ramsesphilios. The white was that of a man’s face. Pale, eyes open, staring up at the stars unblinkingly.
...
There were no signs of blood anywhere except for a small patch of dark red on the front of his uniform, staining both fabric and brass buttons. His still face was calm and emotionless, like that of a statue. His lips were tightly shut. Only the eyes continued to remain open.
We already can gleam a few things about our intruder from these scant bits of evidence.
He was patient enough to have tracked Markos while the guard was all on his own, and had enough time to hide the body in the bushes where (hopefully) no one would find it. We also know that he is stealthy enough and skilled enough in combat to take a trained fighter completely by surprise and land a killing strike that left very little evidence after the fact. The expression on Markos' expression is calm, indicating that there was no struggle and that he didn't see it coming at all.
Wherever this guy is, he has moved on.
treave, how far is the banquet hall from here? The update implies that it's a bit of a ways away. If he is already on the move and has intentions of perhaps assassinating the Lord and Lady, then it's questionable whether we reach them before he does. Worse yet, since we didn't talk to them to begin with, they might be somewhere else by the time we actually get to the banquet hall - they could be off to bed, for all we know.
The cook seems like a better option. Busy kitchen, lots of servants running around there on a night like this. Plus the kitchen is close, so we wouldn't lose much time.
Our brother. Well, given our meta-gaming info, he or someone he knows may even have something to do with this. From an in-character perspective, I'm not sure what Eannos would do in this situation.
Screaming and yelling is another option. But even if the killer is far away, we have no idea who else is actually around and what they can actually do for us. If he is close, I doubt that he tries to kill us - it might blow his cover, and I have a hunch that he's a bit more cautious than that.
Given the situation, I think the best course of action is
A. Please consider this, bros.