In a two-player game (with the priest and gunslinger characters), we are playing the introductory mission (a fistful of dark stone).
At the exploration face, the second revealed exploration token was "!". We drew a High Thread card. And we placed the final enemies. Then, the Growing Dread cards are resolved.
If the first revealed Exploration Token also was "!", then yes, the Final Fight starts. If the first revealed Exploration Token was some other one, you continue playing normally. Only when you reveal the second "!", you draw the High Threat to start the Final Fight.