The famous TV-series Prisoner was first shown in 1979, and then only twenty episodes were intended. The original cast included Val Lehman as top dog Bea Smith, Sheila Florance as elderly, high-spirited drunkard Lizzie Birdsworth and Patsy King as Governor Erica Davidson. The series became so popular that it was extended beyond the first-intended twenty episodes. In the end in 1986, 692 episodes of Prisoner had been shot.

The TV-series became a major employer for Australian actors in the late Seventies and Eighties. Sooner or later, almost every Australian actor at least had had a guest starring role in the show.

Gerda's first appearence in Prisoner was not as Ann Reynolds. She had a small guest starring role already in 1981 - two years before she would become a member of the fixed cast - as Officer Roberts at Barnhurst. Bea Smith had been transferred to this prison by episode 197, and at Barnhurst she encounters the corrupt officer Mrs. Roberts, who is dealing with drugs among the inmates. This character is totally different from the one Gerda came to play two years later. Gerda starred as officer Roberts in two episodes - 197 and 198 - and then left, only to be back again soon enough.

In 1983, Patsy King left the role as Wentworth's Governor Erica Davidson. Meg Morris, Colleen Powell and Joan Ferguson battles for the now vacant position as governor, but in the middle of their struggle against each other the Department suddenly presents the new governor - Ann Reynolds. In the beginning no one seems to like Ann, partly because of her sudden and unwelcome arrival, and partly because of her strict methods in keeping discipline inside Wentworth. At first, Ferguson tries to approach Ann as a potential friend, but the two soon clash. Ann is strict and fair, but not reckless. Quite soon, Ann is respected and liked by all at the prison, except for Ferguson, perhaps. Even most of the inmates respect her.

Ann's best friend at Wentworth become Meg Morris (Elspeth Ballantyne, whom Gerda had acted with already in Bellbird). The two create a solid team and Morris always acts as Ann's loyal supporter. After their famous kidnapping scenes in around episode 500, where they are imprisoned in a booby-trapped house for several days, they grew even closer. Meg Morris grew closer to Ann than she ever was to Erica.

The appealing with Gerda in Prisoner is her portrayal of Ann as firm but compassionate. She was able to receive respect even from the toughest women in Wentworth. When inside her office, with a picture of the Queen on the wall, Ann is the perfect representative of the State and makes it quite clear for any potential troublemaker that she will not take any nonsense whatsoever.

Another fascinating storyline regarding Ann is her bad taste in men. This bad taste is perhaps not good for Ann Reynolds, but it presents the viewer with intriguing mixing of different social backgrounds. Wally Wallace is the happy caveman, and biker-boyfriend Dan Moulton socialises with entirely different people than Ann does. Seeing Ann talking sex with Wally, or jumping up at the back of Dan's motor cycle with a black leather jacket on really gets to you, when you are used to see her in a strict dress behind the governor's desk.

Gerda stayed with the cast of Prisoner until the end in 1986. After Ann finally had got rid of both Ferguson and the difficult Mr. Dwyer, she and Meg celebrates the approval of Ann's prison reforms, at last.