For several years his research was nonexistent, and he didn’t publish any articles. He tried to blame it on the weather. The long drought made fieldwork pointless. His service to the university was lacking as well. When he was asked, one semester, to serve on a course-catalog committee, he stared at the professor and said, “Put my name down if you have to, but if I show up, I won’t say anything, because I frankly don’t care.”

He came to hate the sun. The mocking light of it. It burned the clouds from the sky and cooked the fungi from the forest floors. And it made him want to retreat into the burrow of his bedroom. But now, at last, the hard rains have come again, and the sky is a welcome gray. The ground is so parched, you can almost hear it suckling greedily at every drop. And Jack feels similarly. He isn’t over the loss of Mia—he never will be—but he no longer feels dead himself. He feels thirsty for recovery. He feels ready to live again.

He realizes that his mind has wandered away from the classroom when a student with purple bangs raises her hand. The room is silent except for the rain and the hum of the computer and the scribble of the Montblanc pen. Everyone is looking at him. He clears his throat. “Where was I?” He glances at the screen. “Right. The Great Oxidation Event! It started with ocean-dwelling cyanobacteria. You stir that up with some iron, some volcanic and tectonic activity, and boom—you’ve got the first squirts of oxygen. Soon after that, things get slimy. It started when algae slicked the shoreline. Then this algae began to slowly evolve into things like mosses, lichens, liverworts. These were responsible for boosting organic carbon into sedimentary rocks, which in turn became a primary source of oxygen. Oxygen levels went up and stabilized the atmosphere that supports our lives today. Without moss, in other words, none of us would be alive. Not you, not me, not your cousin Susie, and not your dog Baxter. Plants kick off new life cycles.” He licks his lips and finds a new way to phrase this and really drive it home. “Plants will determine the future of our lives.”

The student with her hand up begins to wave it back and forth. “Excuse me? Professor?”

“Yes!” he says. “Chrissy, right?”

“Missy, actually.”

“Missy!” He smacks his palm against his forehead. “Of course. What is it you have a question about?”

She points to her wrist even though she’s not wearing a watch. “No offense, but I’m going to be late to my next class.”