Already in circulation
A headshot stops them
The group says it first, in episode one. A hit to the head will stop them.

World
The story sits on Salt Lake City, Utah. The Great Salt Lake is real, and so are the streets. The church is not the villain. Crystal Society is a fictional name. How the dead change is something you investigate.
How it takes
Joseph grinds vagrants into cheap meat paste and gives it away like charity. The emptied are brought back to the mill. After hundreds of loops, a key gathers in the gut. White fungal threads in the foundation eat rot and throw rust spores into the air. The key is in the body. The trigger is in the wind.
Already in circulation
The group says it first, in episode one. A hit to the head will stop them.
Still open
Fang Yuan is the question. People in the group treat movies like a manual. He looks at the wound. He looks at search results. No one will swear to it.
Opens in the story
Cannibal paste cycles through the bottom of the city's food. Those who eat to the threshold already have a lock inside them.
Opens in the story
An unknown fungus uses rot as its medium and throws a deformed load of spores. Once inhaled, hyphae follow the blood looking for the key. Anyone who never ate the paste does not turn from air alone.
A fictional name
Control, isolation, thought work, harm to people with no cover. After it was broken, remnants went underground. Joseph is one of those remnants. The name matches no living person or real group in this city.
You might walk into them. They are not the cause.
An old extremist pocket in a closed community. Fang Yuan may stray into them while running. They are not the root of this disaster.
Water, roads, power. Not the villain.
The lawful face after the old order fell: airport, highway, water. The disaster comes from the mill and from particular people, not from the city as a whole.

City to the southeast, lake to the northwest. Salt crust, shallows, Antelope Island. When rust fog clamps onto the city, the lake is still there, pink as an old scar.

After the open, the first food that is still hot. Chips, cola, a hiking pack. Fang Yuan reads the street the way he would read a firing lane. The screaming comes in through the window.

He does not take the front door. The exit he marked is rear right. Fire door, T-junction, off the square, toward houses and a motel.

After the scratch, this place is done too. Gauze, night, the decision to take the Wrangler.

A quarter tank. Cobalt gauges. Search still open. The group still arguing. The skin around the wound looks normal enough to be frightening.

The east evacuation line. By the sunrise in episode three, the rust fog has already clamped up from inside the city. That is not dawn.

The address nailed in the mail. Mill, paste, puffballs, vents. The red pin is eleven kilometers from the restaurant.
Rust is film, dust, scab, spore. Cobalt is for the living. Rust-red is for the dead.
#2C64C4
CobaltJacket, gauges, anyone still alive#8C2D1C
RustSpores, puffballs, hyphae#D45232
Hot rustOutbreak, type still burning#E4D4BF
Bone paperTitles, mail, type you can still read#0C0908
VoidNight, cut to black, before the phone lights