There have been hints of that, but MC doesn't actually know anything about it. It all depends on the choices you've made, the paths you've taken and how you feel about things so far. Based on my reactions to things, I came in not liking the Templars and I know that some of them really hate the Alfar, so I'm inclined to believe Medb - who has made a MUCH more positive impression than the Templars. If I'm playing as the MC there is no part of me that doubts for a second that the Templars would kill Finn, and I have no other suspects. I'm definitely not going back to the city as Neutral toward the Templars - I despised them when I left the city, before I'd met Finn.