How does the infinitive function in the sentence?

Infinitives can be used as nouns, adjectives, or adverbs. An infinitive will almost always begin with to. Exceptions do occur, however. An infinitive will lose its to when it follows certain verbs. These verbs are feel, hear, help, let, make, see, and watch.

Look at the passages where the author describes the isolation and insanity that dr frankenstein has

Im sure its the answer is  4 1 2 3 thats hope i