I've found that encounter in the 3rd map, Ironca, or whatever its name is, it has a red river in it.
Scout Lvl 1: Forest
Scout Lvl 2: Humanoid
Scout Lvl 3: Brigand
Scout Lvl 4: Cottage
I'm assuming that's the one you mean. I don't know if there's any requirement for it, but I do know that if you don't know 'the Cant' then you can't enter. You have two options when entering that area, 'Speak the Cant' and Leave. Hope that helps.