In the third stanza Poe introduces the conflict.  He says that Annabel Lee was killed.  He blames this
on the jealousy of the angels he writes “a wind blew out of a cloud by night / chilling my beautiful
Annabel Lee” (lines 15&16).  He then says “her highborn kinsmen came / and bore her away from
me to shut her up in a sepulchre” (lines 17&18).  Poe is saying that Annabel’s noble relatives came
and buried her in a tomb.  The third stanza lets the reader know what has happened to the relationship
between the narrator and Annabel Lee.