Similar to others who lived in the tunnel, Maggie was a beggar and not much was known about her past. Sometime in the mid-19th century, she was being beaten by five men in the Marylebone Church when the Assassin Jayadeep Mir, who was working undercover as Bharat Singh, witnessed the act of violence and saved Maggie from her attackers. However, as he hesitated with the final blow, his enemy took the advantage to kill him but the old woman tackled the man, saving Jayadeep's life. From then on, Maggie joined Jayadeep's home in the Thames Tunnel and became a mother and a helper to those in need.
Maggie and Jayadeep stayed in the last alcove of the tunnel and looked after each other. The Assassin brought home food and money and taught Maggie to read at night by candlelight. In return, Maggie served as Jayadeep's guide. By 1862, the old woman had already befriended the tunnel dwellers Charlie and Jake, to whom she gave food.