Hess Farm was bought by the red army, presumably when they were also creating the Russian laboratory under the Starcourt Mall. The Russians built a secret basement for the farm, in which they would steal and transport energy from the Hawkins power plant.
Hopper and Joyce found the farm on July 2nd, 1985, where they discovered Dr. Alexei for the first time. However, Grigori had arrived at the farm minutes after them. When they realized he was also in the farm, they quickly tied up the Russians, hid, and waited Grigori to enter the basement so they could ambush him. This did not exactly go as planned, and Hopper and Grigori ended up in a gunfight. Hopper was able to wound him and they managed to escape, taking Alexei with them as a prisoner.