H.H. Holmes, born Herman Webster Mudgett, was one of America's first documented serial killers, known for his infamous "Murder Castle" in Chicago during the 1893 World's Columbian Exposition. His confession, made public in 1896, is a perplexing document that has been scrutinized and debated by historians and criminologists for over a century.

In his confession, Holmes claimed to have killed 27 people, although this number is often disputed, with some researchers suggesting it could be fewer and others proposing it might be more. The confession was sensationalized by the media of the time, with Holmes providing detailed accounts of his murders, methods of disposal of the bodies, and his motivations.

However, the veracity of Holmes' confession has been a subject of debate. Some of the people he claimed to have murdered were found alive after his confession was published. This has led to speculation that Holmes exaggerated the number of his victims either as a form of self-aggrandizement or to confuse the authorities. His motives for the killings, as per his confession, ranged from financial gain to a simple desire to kill.

Holmes was eventually convicted for the murder of his business associate, Benjamin Pitezel, and was hanged in 1896. Despite his detailed confession, the exact number of Holmes' victims remains uncertain, and the true extent of his crimes may never be fully understood.