Edwina's backstory revealed that, unbeknownst to Matthew, she was Judith's mother, her being the product of her relationship with former classmate and current Saint Marie mayoral candidate Victor Pearce, having left Edwina when he learned of her pregnancy. After Judith learned that Victor intended to close down the church's orphanage if he were elected mayor, she enlisted her mother's help in a plot to kill him.
The mother and daughter duo plotted to kill Victor as he went to vote in the election, with the two acting as though they were looking for a fan to replace the broken one in Edwina's office (which Judith had deliberately sabotaged). During this period, Edwina retrieved the knife Judith had hidden in the church storage room and hid by the polls, waiting for Victor to leave the booth to get a pen from Matthew (as Judith had stolen the pen from Victor's booth prior). When Victor started to go back into his booth with Matthew's back turned to him as he went back to his death, the evil Edwina took the opportunity to stab Victor in the back, killing him. Afterwards, Edwina got the replacement fan from the storage room, making it appear that she and Judith had in fact been looking for it and had alibis for Victor's murder.
Edwina and Judith's scheme initially worked, but DI Jack Mooney eventually uncovered both Edwina and Judith's familial relationship and how they had conspired together to kill Victor. After gathering the case's suspects together at the church, Jack exposed Edwina as Victor's murderer as well as how Judith had enlisted her mother in a murder plot against him. After fully revealing Edwina as Victor's past lover and Judith's mother, as well as how the pair had been motivated by a desire to protect the orphanage as well as revenge against Victor for abandoning them, Edwina was handcuffed and arrested along with Judith.