The product of a loving and wealthy Swiss family, Victor is highly ambitious and determined to leave his mark on the world. As a teen he studies alchemy, an outdated pseudoscience. At this point Victor is still relatively naive, captivated by the allure of science. Victor is horrified by his creation: a monster of hideous appearance and proportion. In an attempt to atone for his ambition and excessive pride, Victor becomes obsessed with tracking and killing the Monster yet succeeds only in isolating himself from all human contact. Victor and the Monster serve as doubles of each other, revolving in opposite ways around many of the book's themes. Their relationship is not a simple matter of one character being good and the other evil, however. Rather, the two shift back and forth in terms of morality, with the actions of each being more moral at some times and more objectionable at others.
The Monster is an eight-foot-tall giant Victor Frankenstein forms and brings to life. The Monster is composed of various body parts scavenged from cemeteries and morgues, so he is hideous: his yellow skin "scarcely cover[s] the work of muscles and arteries beneath," and he has "watery eyes" that seem almost of the same color as the "dun white sockets" in which they are set as well as a "shriveled complexion and straight black lips." Born innocent, the Monster is baffled when Victor violently rejects him. Highly intelligent and eloquent, the Monster educates himself, learning to read and write French, but all his learning cannot help him find what he most desires: companionship. After Victor rejects him, the Monster alternates between acts of horrific violence (killing Victor's brother) and touching kindness (rescuing a drowning girl, helping impoverished peasants). When Victor tears apart the mate he had agreed to create for the Monster, the Monster kills Victor's best friend and Victor's wife. No one will accept him because of his appearance. He is doomed to a life of bitter loneliness and isolation.
Walton is the narrator of the frame story that begins and ends the novel. He plays an important role in the plot by confirming the Monster's existence, because he spoke with him, and allowing readers to know what happens to the Monster after Victor's death. He also plays valuable thematic roles. Seeking to accomplish "some great purpose" in life, Walton sets off to explore the Arctic. Walton seeks two things: fame from exploring the Arctic and a friend. His ambition parallels Frankenstein's, while his yearning for friendship parallels the Monster's. He believes he has found that friend in Victor Frankenstein, but the latter dies soon after Walton and his crew rescue him. Finally, Walton serves as Victor's foil, the differences between him and Victor helping highlight Victor's characteristics.
Henry is Victor's closest friend, an easygoing, helpful, and charming young man whom Victor met in childhood. Henry studies languages at the university and nurses Victor through his breakdowns, setting aside his own studies to do so. He displays the attentive, caring, devoted behavior of a true friend. The Monster kills him after Victor breaks his promise to create a companion female monster.
The daughter of an Italian gentleman and Alphonse Frankenstein's sister, Elizabeth has a "gentle and affectionate disposition" even as a child. (In the 1831 edition, she is the orphaned daughter of a Milanese noble whom the Frankensteins adopt after taking custody of her from a peasant family that could no longer afford to support her.) She and Victor grow up good friends as well as siblings (and cousins), and they marry when they are adults. She is pure goodness, as compassionate as the Monster sometimes is, but is innocent and incapable of his violence or of Victor's challenge to morality. The Monster strangles her on her wedding night.
Compassionate and caring, Alphonse Frankenstein and his wife, Caroline, treat everyone well. Alphonse dies soon after his niece/daughter Elizabeth is killed, crushed by the weight of too much sorrow.
A loyal servant and help to the family, Justine is an innocent casualty of Victor's creation. She accepts her fate with remarkable calm. She, like Elizabeth, also serves as a foil to the Monster. Also like Elizabeth, she is given up by her family, but both find a loving home. The Monster, abandoned by his creator, is left without one.