If some compelling fate had said to him, "There shalt thou stand and gaze," he could not have stood more absolutely still, nor gazed more intently.

The spell lasted long: some three or four minutes he stood, watching the place with almost unwinking eyes, like one turned to stone, and within him his mind was searching, searching, to find out, if he might, what thing this could possibly be.
He did not suppose that she would come back.

Neddy Morrison had implied that the condition of her appearing was that she should not know that she was seen.

It was three years since the old man had seen the same apparition; how much might three years stand for in the life of a mermaid?
Then, when such questioning seemed most futile, and the spell that held Caius was loosing its hold, there was a rippling of the calm surface that gave him a wild, half-fearful hope.
As gently as it had disappeared the head rose again, not lying backward now, but, with pretty turn of the white neck, holding itself erect.

An instant she was still, and then the perfect arm which he had seen before was again raised in the air, and this time it beckoned to him.