This morning in Brooklyn, there is rain. It darkens the cement of the sidewalks and slickens the unswept leaves. It annoys the commuters as they hurry to the subways and buses, caught off-guard by such chilly assault after two days of spring-like warmth. It lays a cotton-thin blanket of fog over the snarling pre-work traffic of the BQE. It shortens the dogs’ walks, their owners tugging gently on the leashes, leading them back home.

Today, while the rain taps against the windows of a...