Joan Bulmer is a friend and later lady-in-waiting to Katherine Howard during the first half of Season Four of The Tudors. She has knowledge of Katherine's scandalous past but loyally tries to help Katherine hide ties to her former life, though she does pressure her to give her a position at court.
Season FourEditJoan arrives at court claiming to know Katherine personally; Katherine immediately becomes uneasy on learning the identity of her visitor (4.01). She talks with Joan privately, with Joan hinting to their past history, when the two women lived together in the house of the Dowager Duchess. Katherine visibly wants her to shut up, but she gives in to Joan's request for a position at court. Joan is slightly air headed, not realizing the implications of their rather scandalous past together; nonetheless, she shows Katherine the proper decorum as Queen of England and remains her friend. It is gradually revealed that the two of them were once regularly visited and had passionate sex with two men, Francis Dereham and Henry Mannox, in the Duchess' house.
Unintentionally, Joan gives away details of her and Katherine's sexual history to Lady Jane Rochford, Katherine's principal lady-in-waiting. Unbeknownst to Joan, Jane has a deep dislike of Katherine (as she replaced Anne of Cleves, whom she liked) and is seeking to disgrace her; she uses this information to coerce Katherine into an affair with King Henry's groom, Thomas Culpepper.
Unfortunately for Katherine, Francis Dereham arrives at court and blackmails her into making him her personal secretary (4.04). Dereham foolishly tries to flirt with both Katherine and Joan, but is angrily rebuffed by both; Joan and Katherine become frightened when he starts boasting about having 'known them' when drunk.
The boasting soon leads to suspicions of affairs and Katherine's promiscuity: she is accused of having lied to Henry about her virginity, which makes him put her and her household under investigation (4.05).
Joan is questioned early in the investigation by Solicitor-General Richard Riche. Though reassured that she will not be punished if she tells the truth, the simpleminded Joan is terrified of torture and execution, and immediately gives away full details of her relationship with Mannox and Katherine's relationship with Dereham (who is then immediately arrested and tortured).
While Joan is spared punishment, she is expelled from the court. She stays in London long enough to witness Katherine's deminse: she is sentenced to be executed as Dereham revealed Katherine's adultery with Culpepper. She gloomily meets the eyes of her former friend and gives Katherine a tearful smile of encouragement before the blade drops.