Family

"She told me that that same evening William had teased her to let him wear a very valuable miniature that she possessed of your mother.  This picture is gone, and was doubtless the temptation which urged the murderer to the deed."  (Frankenstein p. 47)

Family plays a very powerful role in Victor's life.  A letter from Elizabeth snaps Victor back into reality after his sickness.  William's murder motivates Victor to return to his homeland.  Victor's loyalty to Elizabeth and his father prevent him from committing suicide.  In the novel, Justine is basically an adopted motherly figure to the family; therefore, Victor can never bring himself to believe that Justine is the true murderer.

In the excerpt above, Victor's father explains the motive for the murder in a letter to his son.  Justine is deemed the murderer because the same locket placed around William's neck was found in Justine's pocket the next day.  Victor refuses to believe the accusations made about Justine because he is completely set that the creature is the murderer.  To me, this seems impossible - how could the creature know exactly where Victor's family lived and where they were going to be?  It may be a coincidence (after all, Victor did see the creature at the site of the murder), but I believe the creature is innocent.  The case made for Justine is more sound than Victor's assumptions about the creature.  In the end, Victor and Elizabeth rely on family loyalty and connections to deny accusations.

For some reason, the accusations and death of Justine remind me of the Pretty Little Liars theme song.  This is a pretty loose connection, but at least the song mentions a locket and secrets.