He winds up taking a job at a food processing plant, and an at-work accident results in him falling into a vat of pickles.
Unfortunately, his only descendant is a thoroughly-modern computer coder named Ben (Rogen) who is basically an alien to Herschel.
The brine winds up perfectly preserving him for 100 years, and when he wakes up his first thought is to find his family.
Based on a New Yorker novella by Simon Rich (who also wrote the script), American Pickle begins centering on Herschel Greenbaum (Seth Rogen) – a laborer who immigrates to America in 1920 with the hopes of creating a new life for himself and his family.