The first disruption was a sound that didn’t belong. It began as a distant, low growl, a vibration felt more than heard, coming from somewhere beyond the thick line of elms bordering the north side of the park. It was a sound at odds with the birdsong and the rustling leaves. The sparrows fell silent. The squirrels froze, tiny statues of alarm on the branches of the oak. Arthur lifted his head, his thermos pausing halfway to his lips. He was a man who had spent a lifetime decoding sounds, and this one spoke a language of urgency.

The low growl climbed in pitch, swelling from a murmur to a sharp, insistent whine. Then came the crunch of heavy tires on the park’s gravel service road, a sound that shattered the morning’s delicate peace. A patrol car, a black-and-white cruiser, emerged from between the trees at the park’s main entrance. Its light bar was flashing, but the siren was silent, which was somehow more unnerving. The red and blue lights spun across the tree trunks and manicured lawns like restless, predatory eyes.

Then another followed. And another.