I could hear his voice, and so I knocked.

There was no answer, but I still heard the voice.

I peeped in.

The man lay on his back in bed, talking brokenly but with spirit, and punctuating with his arms, which he thrashed about, restlessly, as sick people do in delirium.
I slipped in softly and bent over him.

His mutterings and ejaculations went on.