There are many times, in Mary Shelley's Frankenstein, where internal conflict is illustrated. Internal conflict is the conflict which is found within a person. Many times, the conflict arises from what a person wants to do and what the person should do (essentially, the conflict between right and wrong). (On a side note, I have an electronic copy of the text. Page numbers do not exist. I will provide you with chapter number.)
How can I describe my emotions at this catastrophe, or how delineate the wretch whom with such infinite pains and care I had endeavoured to form?
One of the most profound examples of internal conflict is found in chapter five. When the creature first comes to life, Victor is beside himself. He cannot understand why the being he toiled over is so horrible.
A thousand times rather would I have confessed myself guilty of the crime ascribed to Justine...a declaration would have been considered as the ravings of a madman, and would not have exculpated her who suffered through me.
The above quote comes from chapter eight. Here, Victor is struggling with his own confession regarding Wiliam's death. He knows that his confession would not matter and only make him look insane.
“I did confess; but I confessed a lie. I confessed, that I might obtain absolution but now that falsehood lies heavier at my heart than all my other sins."
In the same chapter, Justine shows internal conflict when she confessed to William's murder (although she did was not guilty) in order to gain absolution.
In all of the circumstances, both Victor and Justine are conflicted about what should be done, or has already been done. All of these instances illustrate the theme of either duty and responsibility or justice verses injustice.