Joan Dallimore was the mother of Monica Gallagher. Joan appeared in Episode 9 of Series 5, after having no contact with her daughter in over twenty years. Debbie claimed that Frank and Monica originally told the Gallagher children that Joan was long ago murdered by a jealous lover in Rio de Janeiro, because they didn't want them to meet her. Shortly after her arrival in Chatsworth, it was revealed that Joan had Alzheimers. Joan would later die in the episode after over-dosing on sleeping pills.
Monica's father left Joan when Monica was four years of age. Joan never recovered from the break-up, and would resent her daughter. Joan claimed that Monica would look at her "with his [Monica's father] eyes, ripping my heart out". Joan would take a man named Dennis as her boyfriend sometime after her break-up. However Dennis was sexually abusing her young daughter every night. Joan knew about this, but allowed it to happen because she wanted Monica "punished". When Monica was a teenager, Joan attempted to seduce her daughter's boyfriends, Frank included.
Frank spent Joan's visit worrying that their affair would be revealed and so tried to see how much she was able to remember. Just when he was convinced she was too effected by her Alzheimers to remember, Joan loudly announced to the whole Jockey that once on Monica's birthday she and Frank had had sex. Frank stuttered and tried to cover but Ian and Karen didn't seem convinced.
Joan spent much of her visit loudly worrying about the location of her handbag and losing patience with her mother, Monica threw the handbag to her after finding her propositioning a group of teenage boys in her confusion. The handbag spilt it's contents of many bottles of sleeping pills onto the floor with Joan commenting that she was not going in any care home and had found another way, meaning suicide.
Monica took the pills and hid them, leaving Joan still worrying about where he handbag was at all times but now confused as to why. Monica then took her mother out for a walk, during which Joan revealed that she was now unable to recognize Monica as her daughter. She began talking about Monica's childhood however and admitted that she didn't like Monica as she resembled the husband who left her and had been well aware that her boyfriend Dennis abused Monica as a child but wanted her "punished". Joan then revealed that she wanted her daughter's forgiveness before she killed herself.
Monica tried to seek advice on whether to help her mother commit suicide from Frank but as he had stolen some of the sleeping pills he was unfit to comment. Mandy told Monica that unless she wanted to end up in Strangeways Prison with half her family then it was best left alone however.
Monica ignored Mandy's advice though and returned the pills to her mother's handbag before giving it to Joan. Aware that Joan couldn't recognize her, she said she had spoken to Joan's daughter and that though she couldn't forgive her, hearing Joan admit she was aware of her daughter's abuse meant a lot and she still loved her despite everything.
The next day while the family was at breakfast Monica asked Norma to go and wake Joan. Debbie offered to wake her instead but Monica pointedly stopped her and sent Norma instead who discovered Joan dead surrounded by empty pill bottles.
As Joan's body was loaded into an ambulance Monica took the baby blanket Debbie and Mandy had made and placed it over her face. Debbie later commented that this was a nice gesture but Monica countered that it wasn't really, she hadn't really liked the blanket and asked Debbie not to make another.
Upon seeing a corpse being loaded into an ambulance outside the house, Liam ran over looking worried but Debbie casually told him not to worry as it was "only Nan" causing Liam to shrug and run off again.