In the poem The Raven , by Edgar Allan Poe, the following stanza describes the encounter between the narrator (poet/main character) and the bird which he still does not recognize, yet, has heard "tapping at his chamber door"
Open here I flung the shutter, when, with many a flirt and flutter,
In there stepped a stately raven of the saintly days of yore.
Not the least obeisance made he; not a minute stopped or stayed he;
But, with mien of lord or lady, perched above my chamber door—
Perched upon a bust of Pallas just above my chamber door—
Perched, and sat, and nothing more.
What this stanza means is that at one point the narrator opens his window (flung the shutter) and the bird crept in from the outside. Under a more allegorical perspective, we can assume that the bird, representing melancholy and the past, crept into the life of the narrator as surprisingly as his reality crept into him, making him now a lonely man in the bleak climate of December.