Dexter O'Connell was a convict employed at the Van Ness mansion, hired and kept on-staff by Whitman Van Ness, the master of the house, who, despite his appearance as a kind employer willing to grant anyone a second chance, was truly villainous. Dexter O'Connell met his death at the hands of Whitman Van Ness, who framed O'Connell for several murders and disguised his murder to look like a suicide. O'Connell's spirit remained trapped in the house, along with numerous other ghosts, by Whitman's powerful spirit.
Background
Dexter was believed to be a violent convict and it was rumored that Whitman Van Ness hired him out of the goodness of his heart, because he took pity on Dexter. In reality, Dexter O'Connell was a kind man and Whitman exploited him. After Whitman murdered his own wife and several hookers in his mansion, he framed Dexter and hung him. Dexter O'Connell's death was falsely determined to be a suicide. His spirit was trapped inside the Van Ness mansion, thanks to his employer and murderer, Whitman Van Ness.
Season 7
As a trapped spirit, Dexter O'Connell took pity on Whitman's victims and tried to warn them away before they could be harmed. However, his attempts at warning only served to frighten Whitman's victims and failed at saving any, including Annie and two teenagers (as depicted the episode Of Grave Importance - Season 7, Episode 19). Dexter's attempts to warn potential victims greatly angered Whitman, the more powerful spirit, who threatened Dexter not to interfere again.
Despite Whitman's warning, Dexter couldn't bring himself to stand by, doing nothing to intervene, while Whitman took more unsuspecting victims. So, when two teenagers, friends of previous victims, entered the Van Ness mansion, he tried again to warn them to leave. However, Whitman caught him in the act and proceeded to kill the teenagers before they could escape. Dexter stoically told Whitman that he had enough victims and that Dexter wouldn't stand for it. Whitman turned on him and drained him of his essence, essentially destroying Dexter O'Connell's spirit and wiping him from existence.
Powers and Abilities
He was a gigantic ghost of immense strength who possessed the same power-set as a typical ghost. However, he was still no match for the likes of Whitman Van Ness, a much more powerful spirit.
- Super strength - Dexter could overpower any human. His demeanor also instilled intense fear into those who saw him. He was, though, a "gentle giant."
- Invisibility - He was invisible unless he consciously chose to manifest himself.