Five Parts Per Trillion

Soren smelled it before the first cloud crossed the sun.

He was kneeling in the dirt with a roll of plastic sheeting under one arm, and the smell came up out of the ground and stopped his hands. It was the smell of wet stone. Of a basement after a long winter. Of something old and clean opening up.

"Rain," he said.

Maya looked at the sky. It was still mostly blue. "There's no rain."

"There will be." He pressed a stake into the soft soil beside a tomato seedling. "I can smell it."

Maya stood very still in the row of beans. Then she smelled it too, and her whole face changed. "That's weird," she said. "That's really weird."

"What is?"

"The rain isn't here yet. The water hasn't touched anything yet." She turned a slow circle. "So we're smelling something that hasn't happened."

Soren sat back on his heels. The smell was getting stronger, thick and brown and good, and it was definitely coming up from the ground and not down from the sky. A drop of rain had not fallen anywhere near them.

"It's coming out of the dirt," he said.

They both looked down at the same patch of garden bed, the dark crumbly soil between the seedlings, as if it had spoken.

Maya crouched and put her nose almost against the ground. "Here. It's strongest right here, where it's broken up." She poked the loose earth with one finger. "Where Dad turned it over this morning."

Soren leaned in beside her. The turned soil smelled like a thunderstorm. The hard-packed path two feet away smelled like nothing.

"So the smell is in the dirt," he said slowly. "And it gets stronger when the dirt is broken open."

"And stronger when it's about to rain." Maya sat back. "But the rain hasn't done anything yet. The rain can't be making the smell. The smell is already here."

This was the thing Soren loved and could not always keep up with. She had grabbed the wrong end of it on purpose, just to feel its shape.

"Maybe," he said, "the rain doesn't make the smell. Maybe the smell is always here, and the rain lets it out."

Maya's eyes went to the sky again. The wind had picked up. It came across the garden in a push, and the smell came with it, lifted off the ground and flung straight into their faces, so strong now that Soren could taste it at the back of his throat.

"The wind," Maya said. "The wind before a storm. It knocks the smell loose."

The first drop landed on the back of Soren's hand. Then another, on the plastic, a flat tap. And the smell bloomed, doubled, tripled, rolled up off the whole garden at once like the ground had exhaled.

They did not run for the seedlings. They both knelt there in the rising rain, breathing it.

"Where does it come from?" Maya said. Not loud. Like she was asking the dirt.

Soren scooped up a handful of the wet soil and held it under his nose. It was overwhelming, a wall of it. "Something in here is making it. Something alive. It smells alive." He turned the clod over. "Bacteria. There's millions of bacteria in one handful. Dad said. More than people on Earth, in one handful."

Maya took the clod from him and smelled it and went quiet, and then she said the thing that turned the whole afternoon over.

"How much of it is there, though? To smell that strong from all the way standing up?"

Soren thought about it. The smell filled the entire garden. It had reached him before the clouds. It was, right now, the biggest thing about the world. "A lot," he said. "It has to be a lot."

Maya shook her head slowly. She was holding the wet clod close to her face, and the rain was running down her wrist, and she had the look of someone checking a number against the wrong size of container.

"What if it isn't a lot," she said. "What if there's almost none of it, and we're just really, really good at smelling it."

Soren went still. He thought about how the smell had stopped his hands before a single cloud. Before the rain. Before anyone with eyes would have known a storm was coming, his nose had known.

"How good would we have to be?" he asked.

"I don't know." Maya was almost whispering now, against the soil, against the rain. "Like, find one drop in a swimming pool good. Better. Find one drop in a lot of swimming pools."

The rain came down harder. Soren let it run through his hair and down his neck and he did not move, because something enormous was arranging itself in his chest.

There were dogs with noses a thousand times better than his. There were sharks that smelled blood across a bay. Adults talked about human senses like they were the dull ones, the leftovers, the part of being an animal that people had mostly grown out of.

But this one thing. This one smell, made by something too small to see, in amounts too small to count, the breath of bacteria living in the dark. For this one thing, there was almost nothing on Earth that could beat a kid kneeling in a garden. He had smelled the storm coming through the ground before the sky had finished deciding.

"We're the good ones," he said. "For this. For this exact thing, we're the best there is."

Maya laughed, a surprised wet laugh, and pressed the clod of soil back into the broken earth where she had found it.

The rain came down in sheets now, and the smell rose to meet it, and neither of them reached for the plastic. They knelt in the soaked garden with their faces tipped up, breathing in something the whole sky was making, that almost nothing else alive could even tell was there.