Ethel Mackay, also known as Lady Mackay (née Scrogge) is the main antagonist from the book Shadow of the Gallows by Terry Deary. She is a wife of Lord Arthur Mackay, a former British army colonel, and a mother of Bairn Bruce and Rachel Mackay. They live in Edinburgh, Scotland, where she works as a judge. In the book, mother and daughter together prepare the plan to kill Bairn and his stepmother Kitty Bruce by the legal abuse.
Young Ethel Scrogge falls in love with Bill Twist, an antiquities dealer. However, when she learns he steals antiquities from rich people, she leaves him and falls in love with Arthur Mackay, a British army colonel. Unfortunately, she is pregnant with Twist's child. She travels to Dundee to "see her aunt", gives birth to the baby and sells him to Kitty Bruce, who cares about orphans, for twenty pounds. Ethel then comes back to Edinburgh and she and Arthur Mackay travels to India soon after. Two years later, her next child, Rachel is born in India.
Ten year after Rachel's birth, Ethel returns back to Edinburgh with her family and start to live in the rich part of the town and works as a judge. However, Kitty Bruce visits and threatens her that she will tell her husband about Bairn, the son of her and Twist. Angry Ethel sends Rachel, masked as a young servant with a hat, with a request to a chimney-sweep Bairn is working to. Bairn is send to clean the chimney from inside, although it is forbidden, in Mackay's house where Rachel "finds" and "saves" him. Thanks Rachel, Bairn starts to work for Bill Twist.
Later, the "young servant" brings a request to Twist and Bairn is send to the certain house through the chimney to steal some things. The "servant" watches him and then runs to police. Meanwhile in the house, Bairn secretly listens to the plan of three Fenians who are planning to kill Queen Victoria during her visit in Edinburgh. Unfortunately, when the police arrives and Bairn is revealed, one of the Fenians hit his head, so he forgets everything he heard.
He is arrested and during the trial, Ethel bullies Bairn roughly and doesn't allow him to defend himself. She eventually sentences Bairn and also Kitty, who is accused of killing children, to death by hanging. They are then taken to Edinburgh Castle. Rachel, "unhappy" from his fate, accompanies Bairn and "cares about him", but he doesn't know who she really is. Rachel also pretends to help Joseph Bell, Queen Victoria's personal surgeon, to prove the innocence of Bairn and Kitty, but she is actually coning and misleading him. Luckily, Bell reveals her plans soon.
Thanks Bell, Bairn and Rachel later escape from the castle and even stop the Fenians, as Bairn remembers the night again. Unfortunately, they are arrested again and Ethel is going to sentence them to death, but Bell stops her. He then tells the whole story of Ethel, Rachel and Their evil plan. He also reveals Bairn who his real parents are. At the end, Ethel is sent to Australia for fourteen years and Rachel for seven years.