Theresa Doherty was the mother of Ally and Fergal Doherty. She appeared in Series 8 Episode 21 alongside Fergal after the two of them were forced to flee from their home in Londonderry in Northern Ireland. In doing so, she had to leave behind her other son, Ally, which was something she deeply regretted.
With Fergal attending Waterloo Road, Theresa applies to work in the school canteen. Maggie Budgen, in desperate need of staff, hires her.
Theresa pleas with Fergel to keep out of trouble but Fergal yet again finds himself in trouble with drugs after suppling Harley Taylor with drugs. Theresa is told by Barry Barry that he was given a message to give to her.
Theresa is forced to choose between handing Fergal over to a gang or having Ally, still in Londonderry, be harmed.
She tells Fergal to stay at the school, saying that she will pick him up at 6pm. Unbeknownst to him, Theresa had chosen to give Fergal over to the gang, and the gang leader was coming to the school at 6pm to get Fergal. Nikki Boston goes to the cooler where Fergal was and asks where he's gone. Theresa lies and says he must have gone home.
Nikki insists on going back with Theresa, where they wait for Fergal. When Fergal fails to show up, Theresa admits the truth to Nikki, that they were forced to leave their home because Fergal’s drug dealing had made him some powerful enemies.
Nikki and Theresa rush back to the school just in time to stop Fergal being attacked by the gang leader. The gang leader explained that he was is out for revenge after his 15 year old daughter, Roisin, who was Fergal's girlfriend, died of a drug overdose after Fergal got her hooked on drugs. Fergal explains that she was the dealer, not him, and that he was trying to help her get clean.
The man is arrested and Theresa apologies to Fergal, saying that she didn't know what to do. She didn't want Fergal to be harmed but she couldn't bear for Ally to be hurt.
Fergal realises that they can't keep running away from their problems and turns himself in.
Neither Theresa nor Fergal are seen again