It was howling and beating at the windows outside.

But suddenly there came a sound that rose above the monotonous tumult of it, and Marette started as if it had sent an electric shock through her.

Kent, too, turned toward the window.
It was the metallic tap, tap, tapping which once before had warned them of approaching danger.

And this time it was insistent.

It was as if a voice was crying out to them from beyond the window.