Victor shows up half-frozen and dying on Walton's ship and tells a frankly insane story. Starting with his birth.
He was born in Geneva to parents Alphonse and Caroline Frankenstein, and lived with his adopted sister/ future wife. Creeeepy.
Obsessed with alchemy, he gets some unsettling ideas about science and nature, which blossom into a full-blown obsession with conquering death when his mother dies of scarlet fever only a few weeks before he leaves for college.
Victor attends the university of Ingolstadt, where he's a star pupil of chemistry and natural philosophy.
But academic glory isn't enough: he takes his studies further, figuring out how to create the spark of life in a collection of corpse-parts which—surprise!—turns out to be less awesome in practice than in theory.
He runs away from the monster he's created and is sick for months while his friend Henry Clerval takes care of him.
He tries to put the whole thing behind him, but the monster has other plans: Victor heads home when he learns that his brother William has been murdered.
Victor sees the monster in the woods on the way home when he is locked out of the gates of Geneva for the night; he realizes the monster killed William.
It sounds c-r-a-z-y, so he doesn't tell anyone—even when the Frankenstein family servant, Justine Moritz, is wrongly executed for the crime.
Full of remorse, Victor heads off into the mountains… where he runs into the monster, who makes him listen to a long sob story about how Mommy—we mean, Victor—has ruined his life.
Victor reluctantly agrees to make the monster a female companion.
Once he actually creates the she-monster, though, he has other ideas. He destroys it, dumps the body in a lake, and is promptly accused of murder when he gets to shore.
He gets sick again. This time, he's sick in jail. Fun!
When he recovers (and is cleared of charges), he heads back to Geneva to marry Elizabeth—but not without wondering what it meant when the monster vowed to be with him on his wedding night. (For a genius, he's pretty dim.)
On their wedding night, Victor is all ready to go Rambo on the monster—but the monster kills Elizabeth instead of him. (Obviously.)
Frankenstein Sr. dies of grief, and Frankenstein Jr. swears to pursue the monster all over the world.
Which he does. All the way to the Arctic Ocean.
Near death, he boards Captain Walton's ship. While resting, he tells Walton his story.
He urges the ship not to give up if it ever gets unstuck from the ice, which, considering how well relentless pursuit worked out for him, is probably pretty bad advice.