Henry hadn't gone looking for a leprechaun on purpose today, but he had been hoping to run into one at some point. He had things he needed to be wishing for.
He felt the immortal as he walked through the park and when he saw the little man on the bench, marvelling at some jewellry, he had a feeling-
There was no time for delay. He moved carefully and then he struck, grabbing the being roughly. Then he whispered loud enough only for the little man to hear, "I know what you are."