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?

Context articles: Sarah Elmira Royster
Death of Edgar Allan Poe
Edgar Allan Poe Cottage
Edgar Haynes
John P. Poe Sr.
Edgar Allan Poe (Maryland attorney general)
Edgar Allan Poe: Once Upon a Midnight
Edgar Allan Poe Museum (Richmond, Virginia)
Edgar Allan Poe House and Museum
The Haunted Palace

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.
The death of Edgar Allan Poe on October 7, 1849, has remained mysterious: the circumstances leading up to it are uncertain and the cause of death is disputed.
 On October 3, he was found delirious in Baltimore, Maryland, "in great distress, and ... in need of immediate assistance", according to the man who found him, Joseph W. Walker.
 He was taken to the Washington College Hospital, where he died at 5 a.m. on Sunday, October 7.
 He was 40 years old.
 Poe was never coherent enough to explain how he came to be in this condition.
The Edgar Allan Poe Cottage (or Poe Cottage) is the former home of American writer Edgar Allan Poe.
 It is located on Kingsbridge Road and the Grand Concourse in The Bronx, New York, a short distance from its original location, and is now in the northern part of Poe Park.
Edgar Allan Poe Haynes (May 18, 1866-January 11, 1923) was named after the famous American writer, Edgar Allan Poe.
 He was known variously as E. A. P. Haynes, Allan Haynes, Allen Haynes, and Edgar Haynes.
 He was a Christian evangelist, philanthropist, ardent anti-liquor crusader, and international businessman, who over the course of his lifetime sold insurance, newspapers, cement, and his own expertise in business engineering.
 Haynes also had a widespread criminal record of embezzling, fraud, and failure to pay debts, as well as a history of frequent disappearances, location changes, and turnover in employment in the United States and abroad.
 He died of a brain hemorrhage at the age of 56 in a jail in Vancouver, British Columbia, Canada.
John Prentiss Poe Sr. (August 22, 1836 – October 14, 1909) was Attorney General of the State of Maryland from 1891 to 1895.
 He was born in Baltimore, the son of Neilson Poe and wife Josephine Emily Clemm.
 Poe was the nephew of the poet Edgar Allan Poe through his mother, as well as a second cousin once removed.
 Poe's father was considered an enemy by Edgar Allan Poe, but contacted Poe after his sickness and helped with his burial.
Edgar Allan Poe (September 15, 1871 – November 29, 1961) was Attorney General of the State of Maryland from 1911 to 1915.
 He was born in Baltimore, the son of former Maryland Attorney General John Prentiss Poe.
 He was named for his second cousin, twice removed, the celebrated author Edgar Allan Poe, who died in 1849.
Edgar Allan Poe: Once Upon a Midnight is a one man play starring John Astin as Edgar Allan Poe.
 Astin said, of why he wanted to do a play on Poe, "I feel that Poe, through his own tortured existence, gained deep insight into the nature of the universe, along with an intense love and appreciation for life itself.
 Through this play I want to share that impression with others."
The Edgar Allan Poe Museum is a museum located in the Shockoe Bottom neighborhood of Richmond, Virginia, dedicated to American writer Edgar Allan Poe.
 Though Poe never lived in the building, it serves to commemorate his time living in Richmond.
 The museum holds one of the world's largest collections of original manuscripts, letters, first editions, memorabilia and personal belongings.
 The museum also provides an overview of early 19th century Richmond, where Poe lived and worked.
 The museum features the life and career of Edgar Allan Poe by documenting his accomplishments with pictures, relics, and verse, and focusing on his many years in Richmond.
The Edgar Allan Poe House and Museum, located at 203 North Amity St. in Baltimore, Maryland, is the former home of American writer Edgar Allan Poe in the 1830s.
 The small unassuming structure, which was opened as a writer's house museum since 1949, is a typical row home.
 It was designated a National Historic Landmark in 1972.
The Haunted Palace is a 1963 horror film released by American International Pictures, starring Vincent Price, Lon Chaney Jr., and Debra Paget (in her final film), in a story about a village held in the grip of a dead necromancer.
 The film was directed by Roger Corman and is often regarded as one in his series of eight films largely based on the works of American author Edgar Allan Poe.
 Although marketed as "Edgar Allan Poe's "The Haunted Palace"", the film actually derives its plot from "The Case of Charles Dexter Ward", a novella by H. P. Lovecraft.
 The title "The Haunted Palace" is borrowed from a poem by Poe, published in 1839 (which was later incorporated into Poe's horror short story "The Fall of the House of Usher").