Dr. Alexei, portrayed by Alec Utgoff, was a recurring character in the third season of Stranger Things. He was a Russian scientist involved in developing experimental technology to open gates to an alternate dimension, similar to the one previously encountered by Hawkins Lab in the US. After several unsuccessful attempts to open these gates within the Soviet Union, a secret operation was launched to infiltrate Hawkins, with the aim of exploiting any remaining traces of the original interdimensional incursion. Alexei played a crucial role in this operation.