Answer: He thinks it is a visitor.
In the first stanza of the poem "The Raven," the speaker hears a tapping at his chamber door around midnight. Wondering who could be at that hour, he assumes it is a visitor. The stanza says:
<em>Once upon a midnight dreary, while I pondered, weak and weary,</em>
<em>Over many a quaint and curious volume of forgotten lore—</em>
<em>While I nodded, nearly napping, suddenly there came a tapping,</em>
<em>As of some one gently rapping, rapping at my chamber door.</em>
<em>“’Tis some visitor,” I muttered, “tapping at my chamber door—</em>
<em>Only this and nothing more.”</em>