Warning! Major spoilers for The Haunting of Bly Manor below.
A plague doctor is hidden in the background of many scenes in The Haunting of Bly Manor. He's eventually revealed to be one of the many ghosts that haunt Bly Manor. But he's more than just an anonymous ghost — he has important ties to the history of the house.
The Haunting of Bly Manor is an old-fashioned ghost story. American Dani (Victoria Pedretti) travels to England and becomes a governess for orphaned children Miles and Flora. She quickly realizes that something is not right with both the kids and the house itself — each are haunted by ghosts. As it turns out, some of the ghosts the haunt Bly Manor have been around for centuries.
Aside from the lady in the lake herself, the plague doctor is the oldest ghost residing in Bly Manor. He appears often in the background of the show, more than any other ghosts. Let's take a look at the significance of the plague doctor ghost's presence in The Haunting of Bly Manor.
The Haunting of Bly Manor may be a follow up to The Haunting of Hill House but each series tells its ghost story in a very different way. Hill House focuses more on the haunted past of the Crain family, and Bly Manor is about the haunted history of the manor itself. That's where the plague doctor eventually comes in. Episode 8 of the series, "The Romance of Certain Old Clothes," dives into the history of the home and its original residents. In the 17th century, Viola (Kate Siegel) was the original lady of Bly Manor. However, she got sick and was eventually murdered by her sister, Perdita. As a spirit stuck in a limbo, Viola watched her sister marry her husband and steal her life. That, in turn, caused Viola to become a murderous and vengeful spirit.
Viola's spirit remained on the grounds and she haunted every resident that came after her. After her family moved out of the manor, her previous home became a quarantine location for a local plague outbreak. She wandered throughout the house and a doctor caring for patients happened to cross her path. In her endless and blind rage, Viola killed him. The Haunting of Bly Manor reveals that anyone who dies on the grounds is cursed to remain there after death.
The spirit of that doctor became the plague doctor ghost that lurks in the background of many scenes in The Haunting of Bly Manor. He means no harm to the current residents of the home. His presence is more a reminder of how far back the house's haunted history goes. A plague doctor's uniform is very reminiscent of the times. Their masks included a beak at the nose so the wearer could stuff herbs in it to help with the putrid scent of death. The majority of The Haunting of Bly Manor takes place in the 1980s, and those masks had been out of style for centuries. The intentional and frequent placement of the plague doctor ghost in the background is simply a clue that Bly Manor's tragic and haunted past is deeper than the audience might realize.