Basically, the "hard" part of the episode is going to be one of the following:
In RPGs, there's often a temptation to make all three of these the hard part, and the result is adventures that turn into long slogs. By making only one of them the real problem, pacing stays pretty sharp, and the formula becomes MUCH more usable. If the problem was ALWAYS that the monster was unknown then every show/game would be about research, which would get dull fast. Ditto the other hard points. Shifting emphasis between these three consistent points (Research, Investigate, Apply) gives you the benefits of consistency while still providing versatility.
- Finding out what the creature is (and by extension, its weakness)
- Get their hands on whatever they need to exploit the weakness (get the arcane widget, find the body, find the lair)
- Applying the fix (Actually shooting/burning/stabbing/whatevering the thing, performing the ritual or the like).
If you like you can read the rest here.