For only at low spring-tide could it be reached from the land, and then the flood rose far up the cliff, covering all the shingle, and filling the mouth of a dark cavern.

Had her mother gone to that cavern?
It was impossible to see, so utterly was the cliff shrouded in shadow.
Shivering with cold and excitement, Grace crouched down, and gazed into the gloom, till her eyes swam, and a hundred fantastic figures, and sparks of fire, seemed to dance between her and the rock.

Sparks of fire!--yes; but that last one was no fancy.

An actual flash; the crackle and sputter of a match! What could it mean?
Another match was lighted; and a moment after, the glare of a lanthorn showed her mother entering beneath the polished arch of rock which glared lurid overhead, like the gateway of the pit of fire.
The light vanished into the windings of the cave.

And then Grace, hardly knowing what she did, rushed up the beach, and crouched down once more at the cave's mouth.