Can't quite figure out what I'm supposed to do here. I saw the letter in the greenhouse, got the nightmare vine and the elixir of mental strength. I'm stuck in the room where you get the elixir, I can get by the guard in the hall outside with invisibility, but I can't get through either of the 2 doors there. I'm assuming the templar's room is on the other side, but I'm at a loss as how to proceed.