Miss Hartigan was matron of the St Joseph's Workhouse (a job for which she showed great dislike). Some short time prior to Christmas 1851 she met the Cybermen and agreed to help them achieve their goals in return for the promise that she would be heralded when their plans were accomplished. She was also protected by a guard of Cybershades who drove her horse and coach.
When the Reverend Fairchild was killed, Miss Hartigan went to his funeral and set the Cybermen on the mourners, capturing the workhouse owners and killing the rest. The survivors were fitted with earpieces and told to bring their children to the Cybermen's base of operations.
They led the children to a factory by the docks and made them work the machinery to generate electricity so that the CyberKing would rise. Miss Hartigan killed the workhouse owners and the Cyber-Leader told her she would be converted into the CyberKing. She realised they had been planning to betray her the whole time and tried to refuse to be converted but was forced into it.
However, once converted, Miss Hartigan's superior mind gained control over the Cybermen's technology. She not only killed the Cyber-leader but also assumed leadership over the others. Shortly after this, the Cyberking rose out of the Thames and attacked London with Miss Hartigan as the "brain" of the vessel.
The Tenth Doctor then used a device made from Infostamps to break the link between her and the Cybermen. She saw what she had become and, overcome with remorse and horror, destroyed both herself and the Cybermen in a suicidal attack. (TV: The Next Doctor)
Mercy Hartigan was cruel, callous and sadistic in her interactions with others, especially men, for whom she seemed to harbour a misandrist hatred. She would almost always slip sexual references and innuendoes into whatever conversation she was having, further underlying her hatred of men in general. Hartigan’s sadism and misandry were best displayed when she took pleasure in watching the mourners get massacred, testing the EarPods on Scoons, Fetch, Cole and Milligan and then killing them afterwards. She showed a complete lack of empathy in these instances and was utterly ruthless. When the CyberLeader opted to convert her, he described her mind to be riven with 'anger and abuse and revenge'.
She panicked once she realised the Cybermen intended to convert her but once her mind took control, she appeared to have gone even more insane than before. While she retained her sadistic nature and her misandry, she became extremely arrogant due to her enhanced intellect and new powers. She attacked London as a demonstration of her power and greatly underestimated and mocked the Doctor during their confrontation.
When the Doctor broke the Cyberconnection linking Hartigan to the Cyberking, her mind was "opened for the first time in far too many years". In a moment of clarity, Hartigan became horrified by what she had become and killed herself along with the Cybermen. (TV: The Next Doctor)
Following her conversion into the CyberKing, Hartigan's intellect was considerably enhanced. She claimed to be able to see "the stars, the worlds beyond, the vortex of time and the whole of infinity itself". The Doctor himself admitted that Hartigan had "one of the greatest minds on Earth".
The cybernetic "crown" she wore served as an interface between Hartigan and the Cybermen's hive mind. Through this, she could exert full mental control over individual Cybermen, Cybershades as well as the massive Cyberking robot. The crown also contained a weapon which fired a deadly beam powerful enough to completely disintegrate Cybermen. Hartigan used it to kill the Cyberleader after he threatened to disconnect her from the throne. Even after the link was severed, the "crown" enabled Hartigan to disintegrate herself and the other Cybermen and cause the CyberKing to be destroyed. (TV: The Next Doctor)
Behind the scenes
- During the podcast for The Next Doctor, Russell T Davies (the writer of the story) confirmed that Miss Hartigan was a victim of sexual abuse and that is why she sexualises every conversation and scenario she is in. This also explains her cruel and sadistic attitude toward men. However Davies felt that especially for a Christmas special this aspect of her would only be lightly touched upon for the safety of a young viewing audience.[additional sources needed]
- When Miss Hartigan tests the EarPod's effectiveness she puts the Cybermen through an exercise, ordering them to turn right and left. Similar control of the Cybermen is enacted by Mr Crane as well as Missy, who also order their troops to do the same dance.
- Mercy's proclamation of "I am the CyberKing and you will obey me" is similar to the Master's catchphrase, "I am the Master and you will obey me."