Mrs. Lomax lived with and looked after her middle-aged, asthmatic and mentally challenged son Martin and desired to kill him and herself. She hated Martin for putting his father into prison despite the fact he sexually and psychologically abused Martin, as she missed her husband. She would be enraged when their neighbour Dick from the flat above would play loud music and she would beat on the ceiling to tell him to stop. When Dick came down to confront her, Mrs. Lomax would direct his attention to Martin and tell him to be a man and stand up to him while also hoping the neighbour would kill them both. Mrs. Lomax became concerned when Martin would constantly talk about a centipede with 12 people, not knowing what that meant. She called Dr. Sebring to address this who claimed it was a result of his father's abuse. Despite this and the clear fact Dr. Sebring was attracted to Martin, she still remained apathetic to her son's suffering.
One day, Mrs. Lomax attempted to kill Martin in his sleep with a knife. But when she discovered he was not in bed and he walked in just after, Mrs. Lomax proceeded to slit her wrists with the knife. She then discovered Martin's scrapbook containing pictures and drawings of The Human Centipede (First Sequence). Disgusted by his obsession at such an appalling concept, she tore the scrapbook to pieces. She then tried to remove his pet centipede, but the enraged Martin grabbed her and pulled her head towards the tank where his centipede then bit her in the face. As she screamed in agony, Martin beat her head with a crowbar repeatedly until her skull was completely caved in. Martin then took his mother's corpse and sat it at the kitchen table where he sat down with it and ate dinner. He then used her body to trick Dick into coming downstairs and get captured.