"Tenant in 2B just called. There's mold growing down the side of the building outside her kitchen window." That's the call a property manager makes on a Tuesday morning, and by the time anyone walks out to the parking lot to look, the streak is three units tall — a black line running from a bathroom vent on the top floor down past the kitchen window of 2B, all the way to the trim above the ground-floor windows.

Walk out to the pump island at six in the morning, before the first customer pulls in. The concrete under the dispensers is darker than the concrete twenty feet away. There are halos around each pump base. There are black scuff arcs where tires pivoted. A long dark teardrop runs from one pump out to the drive lane, like somebody dragged a wet rag in a straight line.

It's 6:15 a.m. and the day cook just opened the back door. The hood fan upstairs has been off for six hours. Out here in the alley, the wall under the exhaust vent has a dark vertical stripe running down it — starting somewhere near the roofline and fanning out toward the dumpster pad. Up close, the streak looks almost waxy. The smell is old fryer oil mixed with something stale, faintly sweet.

You stand at the curb on a Monday morning, coffee in hand, and look up at the awning over your shop entrance. Six weeks ago, it was clean. The crew came out, sprayed it down, and said it would last the season. Now there's a faint green tint creeping back along the front edge. A dark streak running down from where the awning meets the brick. By the time the lunch crowd shows up, you'll be hoping nobody notices.

You run a hand along the top rail of the deck, and a fine white powder comes off on your palm. The boards look hazy in the afternoon sun — flat, dusty, slightly faded against the part still shaded by the table. You hose it off, and the boards look right for an hour. By the next morning, the haze is back.

You walk out to the patio with a coffee in hand, and there it is — a streak of orange along the south edge of the concrete that wasn't there last weekend. It doesn't look like dirt. Doesn't wipe off with a wet rag. Closer to a rust-colored tea stain than a smudge, and it's clearly soakedintothe concrete rather than sitting on top.

A truck rolls up, a guy drags a pressure washer hose up an extension ladder, and ten minutes later, he's on the ridge of your roof blasting down the dark streaks like he's washing a sidewalk. Water runs off the eaves in dirty sheets. The black is gone. He hands you a bill and drives off.

You are walking around the side of the house with a microfiber cloth, ready to wipe off what looks like a patch of dirt or mold on the lower siding. The dots are everywhere — hundreds of them, maybe a thousand, scattered across the bottom four feet of one wall like somebody flicked a wet paintbrush. You press the cloth against one. Nothing. You scrape with a fingernail. The dot is still there, with a smear of glossy black residue around it.

You stepped out of the house barefoot, walked across the pool deck on your way to the cover, and almost went down. Same spot, same time of year, same hose-down two days ago. The deck looks clean. Your soles say otherwise.

Pull into your driveway, look up at the gutter line, and there they are — dark vertical streaks running down the front face of the gutter, evenly spaced, almost decorative. Like someone took a wide brush and dragged vertical bars across the white aluminum. The siding is clean. The roof is clean. But the gutters look like they have been wearing the dirt for a decade.

You walk past the side of the building after a wet weekend and notice it for the first time. A pale, almost dusty film smeared across the brick about three feet up from the ground. It wasn't there last month. You run your finger across it and it leaves a chalky white streak on your fingertip — like sidewalk chalk, but finer. Brush at it with your hand, and most of it falls off. A week later, it's back, in roughly the same place, after the next rain dries off.

You drive past the office building every morning. Black streaks run halfway down the north wall, dark stains spread under every HVAC penetration, and a green tint creeps up from the foundation. Then you turn the corner into your subdivision. The houses look fine. Same neighborhood, same humidity, same weather. The office building always looks worse.

You paid for a pressure wash. The crew showed up, blasted the roof, the siding, the patio — the whole property looked like a different home by the time they pulled out of the driveway. Six weeks later, the green tint is back on the north side of the house. Eight weeks in, the patio is starting to feel slick again. By the third month, the roof streaks are visible again from the driveway.

It's the first warm Saturday in April. You are standing in the driveway looking up at the roof, and they are back — those long dark streaks running straight down the shingles. They were not this bad last year. You can tell by how far they reach now, past the chimney, almost to the gutter line. The neighbor's roof has them, too. So does the one across the street.