Inductive reasoning, if thats an option
You did not provide the excerpt but in the end Jekyll was not able to permanently resist. It was implied that he was actually Hyde deep inside and that Hyde is the one who will overtake and he won't be able to come out again. In the end he dies as Hyde and people find out what happened out of letters that he sent while he was sane.
Answer:
The last foot (the anceps) always consists of two syllables so mark it so immediately. You can
regard the very last syllable as an unknown vowel length and mark it as an X (it will normally be
pronounced long no matter what)
2. The second to last foot is almost always a dactyl so mark it so immediately
3. The first syllable of every line of poetry is long no-matter-what so mark it so immediately.
4. The thesis (first syllable) of a foot is always long
5. The arsis (the second half) of a foot will either be one long or two shorts: there can be no
mixing and matching in the second half of the foot
Explanation: