You sat quietly in a field of grass. A light and warm breeze blew across your face and set the blades of grass in motion. The sun was slowly setting behind the horizon and your eyes were closing.

Suddenly, between all that wind and the scent of nature, you heard a quiet whistle. The softest. But loud enough to reach your ears. You have a feeling you've heard it before.

Despite your doubts, you whistled back. The sound rang out once more. But it's impossible.

It's just a wind, right?