The Russian scientist kidnapped by Jim Hopper and Joyce Byers in season 3 of “Stranger Things” is Alexei. He works on the Soviet machine beneath Starcourt Mall, the device intended to reopen a gateway to the Upside Down.
Hopper and Joyce capture Alexei after discovering the Russian operation in Hawkins. Because Alexei speaks little English, they take him to Murray Bauman, who can translate. Alexei explains that the Soviet machine works only in Hawkins because the original gate has left the barrier between dimensions unusually weak there.
Although initially treated as a hostage, Alexei becomes an unexpectedly sympathetic character. He enjoys American treats, especially cherry Slurpee, and becomes eager to escape the Soviet project. His story ends at the Hawkins Fourth of July fair, where the Russian enforcer Grigori fatally shoots him.
Alexei is played by Ukrainian-English actor Alec Utgoff. Season 3 premiered on Netflix on July 4, 2019, matching the fair’s central role in the season’s climax.