Headache was once a Memory hunter who actively ran with the Errorist movement. He was a target of S.A.B.R.E. Force and bounty hunters like Olga Sedova, the latter mentioning once that she was unable to catch him because he was "young and quick on his feet". He was eventually caught by S.A.B.R.E. Force and taken to the La Bastille prison.
While in captivity he was subjected to the prison's "program", the latter of which may have left him scarred and disfigured. He managed to escape eventually, but would later give up Memory hunting altogether. However, he would still remain loyal to the Errorist cause.
The Leaking Brain
Officially out of the Memory hunting and Errorist movement, Tommy set up a legitimate business down in Depp Paris's Slum 404. He established a bar, he called the Leaking Brain in an abandoned freighter ship that was surrounded by the shanty town built up by the inhabitants of the slum.
The freighter ship kept the establishment above the sea levels that had risen following the global climate change. The Leaking Brain was a safe haven for people from all walks of life (but particularly attracted Memory junkies) and a "safe house" for Errorists and Memory hunters on the run from S.A.B.R.E. Force.
When a "lost" Nilin Cartier-Wells wanders down into the slums and visits his bar, the Leaking Brain, Tommy befriends her and later tells her of the Errorists. She would take up their cause and become one the infamous members of the group besides Edge.
Events of Remember Me
When Nilin is captured by S.A.B.R.E. Force, Headache heads for her Safe House and retrieves her "combat skin" and hunter's glove. After Nilin escapes from the Bastille, Edge tells her to head for Headache's bar. When she arrives, Tommy is quick to hug her and make jokes despite her unfamiliarity with him.
He brings her up to speed on current events within the Errorists, but is hesitant to share the details of his imprisonment in the Bastille. As she is readies herself, Headache warns her about Olga and is caught off guard when the bounty hunter manages to sneak inside his bar and attack Nilin. He attempts to stop her but Olga knocks him out.
When he comes to, Nilin has remixed Olga and made her an ally. Relieved, Headache almost gives Nilin's actions away to Olga, but the he is quick to revise his statements. Later, after the Saint-Michel dam is opened by Edge, Headache's bar is attacked by Leapers forced into the higher areas of the Slums.
Nilin arrives in time to help him fight them off, but the damage to his bar is severe. He upgrades her glove with Junk Bolt and shows her a passage down into the sewers, he also warns her of a storm coming and asks her to be careful that it doesn't swallow her up.