Ariyan locates me multiple times, so naturally...

>assas investigate ariyan
You grip your amulet and concentrate on Ariyan. You are immediately answered with a sharp voice that says, "Ariyan is not targeting you. Please stop wasting our time."

OK, so it's not him.

Except that about 5 minutes later he attacks me, I kill him and get "Ariyan had been sent to kill you, but he has clearly failed. Rest easy... For now."

Not sure if its a problem with "investigate" or if he was locating me in preparation for the possibility of my becoming his next target, but the latter seems unlikely.