He went quickly up the three wooden steps, turned the knob, and pushed it open--very softly this time.

No one appeared.

But, as he stood on the threshold, while the pupils of his eyes dilated to the gloom of the hall into which he looked, his ears seemed to detect somewhere in the house a muffled footfall and the sound of another door closed softly.
He stepped inside and called.

There was no answer, but above his head a board creaked.

He started up the stairs in front of him, and, as he did so, he seemed to hear cautious steps across a bare floor above.