Swallows dive-bomb the park, picking insects as they rise out of cooling grass. Jake dodges when they strafe by his knees.

Consider the eye of the predator bird: an instrument hundreds of millions of years in development, perfected while you were still a tree shrew looking out both sides of your head. Forget what it’s like to be a bat. Birdsight, like the Hubble, strains photons bouncing gnatwise from the deep field of dusk.

Jake’s headphones have stopped working. He pulls them off and runs on, puffing, a red-faced struggle to stay out of the ranks of the old and sick.