In The Mystery of the Torn Parachute, Mrs Williams was the sister of the bank cashier Lynsdale who absconded with fifteen thousand pounds.
Mrs Williams was a widow who lived with Lynsdale and kept house for him. Some months before Lynsdale's crime, Mrs Williams left London and proceeded to Morayshire where she rented Dalglennie house on Strathspey, near Tomindalloch. Shortly after Lynsdale absconded with the money, he had mailed her a parcel which presumably contained a large portion of the stolen money. Later, Lynsdale laid a false trail to France and then flew back and jumped by parachute over Morayshire to be picked up by Mrs Williams in her Austin. Her movements had, however, been noted by motorcycle anti poaching patrols managed by Captain Mackenzie, who was able to put Biggles on her trail. Although her eventual fate was not described in the story, it can be assumed that she was arrested with Lynsdale and probably tried as an accessory.