One of the most intriguing aspects of Stranger Things Season 3 was the the Mind Flayer's (i.e. Vecna's pet) cult in Hawkins, Indiana. It was led by Billy Hargrove when the teen got corrupted early on, just like Will, following a car crash near the dilapidated Brimborn Steel Works. The hive mind's co-optation of others, eventually melting them down into goo, made it an extremely scary proposition for fans of the show.
This combined meat mass allowed the possessed, aka the Flayed, to form the giant Spider Monster in the season finale. The creature represented the essence of the Flayer in the real world, as it couldn't fully come through Vecna's rift from the Upside Down. However, while the show didn't reveal that much about the cult kidnapping folks and how sneaky they were in the shadows, the Stranger Things: Summer Special one-shot detailed how brave and twisted they actually were.
This story (by Keith Champagne, Caio Filipe, Dan Jackson and Nate Piekos) focused on the two fan-favorite goofy cops working under Hopper: Powell and Callahan. While Season 3 didn't feature them much, this story showed they were indeed working behind the scenes. They ended up at Doris Driscoll's home, investigating the trouble in her basement after Nancy and Jonathan found something sketchy with the rats there.
Unbeknownst to the cops, the rats were eating fertilizer and turning into a bio-mass to move around town to assimilate more organic beings. Powell and Callahan were also clueless that Billy was tracking them after they snooped around the factory. By this time, Doris was under the Flayer's thumb, which led to her making up excuses to throw the cops off their trail. Doris drove down to the factory, then left it, walking back home. This allowed other Flayed members, such as Tom and Bruce to attack the car. Other members rushed out, but a dazed Powell thought he was sick as he came to. He sped off, not wanting to fight any of the townsfolk, thinking they were having a weird sex party.
It's understandable as he was groggy, but it confirmed the citizens were abducting and making people their pawns. Ultimately, this entire one-shot was a deleted scene because right after this, Doris would get taken to the hospital from eating fertilizer. It led to her, Tom, Bruce and all the others turning into goo and giving the creature its final form. Ironically, Callahan and Powell ended up at Starcourt Mall when the monster was unleashed.
And yet, Powell and Callahan failed to see the giant beast in action against Eleven and her friends. It summed up their ineptitude towards the body snatching and how this incompetence almost enabled the shifty cult to end Hawkins that night, which would have happened were it not for Eleven's heroics, and Billy's redemptive sacrifice.