A feeling of mystery is an effect caused by the rhyme in this stanza.
Up to the 4th verse, the stanza follows a syllabic rhyme ABAB pattern where final words end with similar vowels sounds. This arrangement provides musicality as well as a sense of calm given the use of natural visual imagery.
The 5th verse continues the rhythmic pattern, although it already creates tension by introducing a strange ocurrence "the sound of a hound in the distance".
Verse 6th then ends the stanza by breaking the rhyming pattern maintained and leaving the reader with a sense of mystery and tension about the unfolding of events.