- "I have yet to meet the man who could better me."
- —Agatha to Elizabeth Warleggan
Agatha Poldark was the great aunt of Francis Poldark, Verity Poldark and Ross Poldark. She had extensive knowledge of the Poldark family history and claimed to have witnessed six generations of her family, starting with her own grandparents.
Agatha was born in 1697. She was presumably a spinster, since she was known as "Miss Poldark", and probably served as housekeeper for some time until Verity came of age. She had a lack of contemporary family members as opposed to potential status as a widow.
Agatha frequently acted as though she was deaf, and while she may be hard of hearing, she certainly heard more than she let on. She was known for speaking her mind and guards many family secrets.
Agatha became very close to Elizabeth Warleggan, the wife of her late great nephew, Francis Poldark. She provided advice and company for her, particularly in times of trouble. However, she was unhappy about her second marriage to George Warleggan.
She accepted George's tendency for scheming and was unafraid of standing up to him. She supported her great-great nephew's abundance of rejecting George and became very close to him.
She adored Verity and was joyed when she would return to Trenwith. She knew the true parentage of Valentine Warleggan, something which she would hint at. She was treated poorly by George, who was unhappy by her presence and outspoken ways. She was a staunch protector of her family and was hurt when Ross would no longer come to see her at Trenwith, even saying he was no longer part of their family anymore.
However, she knew he and George were far from friends and was delighted when her great-great nephew informed her that Ross missed her, returning the same sentiment. She did not know that Ross had made a deal with George that he would stay out of his life provided that George treated her and Geoffrey Charles well.
She showed defiance against the idea that the Warleggan family name should replace the Poldark name at Trenwith. She hoped that her great-great nephew would return Trenwith to the way she thought it should be, even supporting him when he refused to change his name to Warleggan and stop seeing his extended family, telling him "quite right"!
Agatha continued to be treated poorly by George and they both enjoyed annoying each other with snarky remarks. She stayed at Trenwith when her family went to stay at Warleggan House for a while, where she was poorly cared for in her cold house. Ross went by to see her where he told her carers that they should care for her better.
When George returned, Agatha and George's relationship had not changed. Agatha was about to celebrate her birthday, and was very excited about having a party. However, when George told Agatha, who was preparing for her party, that she wouldn't have one, Agatha was devastated. She wanted to hurt George in the way she was, and told him that Valentine was not his child. George was now upset as she was, but was in shock and walked away.
The stress of their argument deeply affected Agatha, who felt sudden pain. When Elizabeth found her, she kept apologising for telling George. Elizabeth wasn't certain what she meant, while Agatha continued to experience pain while she became weaker and frailer. While Elizabeth asked her what she meant, Agatha passed away in her chair, holding Elizabeth's hand.
Elizabeth was upset by her death, while George, who was still in quiet shock from what Agatha had told him, said nothing. The news of her death upset her family in Nampara, with Ross calling Agatha his "beloved aunt", and was saddened that she had no Poldark family at her side when she died.
George had arranged a secret funeral with the usual lack of care, and when Ross found out about the poorly arranged funeral, he demanded that he be allowed to bury her, giving her the loving burial she deserved.