Question: Which event in Edgar Allan Poe's life has remained mysterious, prior to which became engaged to Sarah Elmira Royster Shelton, and was soon found delirious in Baltimore and in need of assistance?
Sentence (from "Sarah Elmira Royster"): Sarah Elmira Royster Shelton (1810 – February 11, 1888) was an adolescent sweetheart of Edgar Allan Poe who became engaged to him shortly before his death in 1849.
Relevant evidence: Yes