In Episode Two of Season Three, Chapter Two: The Mall Rats, the town of Hawkins catches a fever for the grand opening of the Starcourt Mall. The team is still trying to unravel the mystery of the strange occurrences happening in the town. The episode starts off with Billy waking up from a nightmare about his time in the Upside Down, suggesting that the Mind Flayer has some kind of hold on him.

Max and Eleven are bonding over the mall and shopping, while Mike, Will, Lucas, and Dustin are on their own mission to uncover the truth. The boys suspect their science teacher Mr. Clarke, is connected to the strange signals they intercepted. They try to steal his files but end up getting caught by him. Mr. Clarke explains that the signals are coming from a secret Russian communication network.

While investigating the mall, Steve and Robin discover a secret Russian code hidden beneath a movie poster at the theater. They deduce that the Russians have some sinister plans in the works. Meanwhile, Nancy and Jonathan are investigating the strange sickness that is causing rats to explode and seagulls to behave erratically.

Back at the pool, Billy is spotted by Mrs. Wheeler, Mike’s mom, who is clearly attracted to him. Billy acts strange and flirty with her, showing that perhaps the Mind Flayer has a hold on him. After a day at the mall, Eleven and Max visit Hawkins Fun Fair, where Eleven uses her powers to win a giant stuffed animal for Max. While there, Eleven has a traumatic vision of Billy being attacked by the Mind Flayer, and then collapses.

The episode ends with Dustin, Mike, Lucas, and Will trying to decode the secret Russian message again using the Cerebro, a device that amplifies telekinetic powers. They finally manage to decode the message but discover that it is a message about the “Key” and “The American,” which clearly points out that something major is in the works.

The episode concludes with a group of people who would seem to be Russians heading to Hazmat suits and opening the gate to the Upside Down.