A continuation, suggested by the comments on Part 1 - thanks for the contributions!

Anna and Sharon talked for a long time, snuggled up in bed together.

“How do you feel about your stepsister Sue, now?”, Anna suddenly asked.

“I almost feel sorry for her”, said Sharon. “Isn’t that stupid? To think that money and power could twist a person that much…!”

“What do you think is going to happen to her now?”

“Prison, probably. Especially if we push the kidnapping aspect. She had me a prisoner for months…”

“What if we didn’t? What would happen if we dropped the charges, just stuck with the attempted assault at the end?”

“Why on earth would we?”

Anna whispered into Sharon’s ear. Her eyes went wide, then she started roaring her head off…

At the police station, to Sue’s amazement, both Anna and Sharon refused to press charges for kidnapping. After all, who would believe them anyway? There had been some rumours going around about Sharon being handicapped in some way, but they obviously weren’t true… were they?

In the end, Sue was let off with a caution, as long as she formally apologised to those involved. She immediately did so to the police officer who attended the incident; he accepted her apology.

She then went to apologise to Anna and Sharon. They insisted that she apologise to them at the flat, as it would mean more to them…

It was only when the chloroform-soaked rag was rammed over her mouth that she realised what was really going on. Her eyes went wide with terror, then she slumped to the floor, unconscious.

Anna and Sharon took their time getting Sue ready.

Anna had made sure the food was back to normal, with a slightly stronger dose of laxative built into it. They also this time fitted Sue with a vibrator.

Remembering how Sharon was released, they also sealed the mittens into the arms of the romper suit, so they couldn’t be removed.

The unconscious Sue was gagged, and a mask was sealed over her mouth, like had been done with Sharon before. Unlike before, however, superglue was mixed in with the adhesive holding the mask on. Sue was gagged for life…

The crackling sound of her plastic romper moving as she awoke told Sue what had happened to her, and she started crying uncontrollably, frantically pulling at her baby harness, then trying to get her mittens off. She also ran her mittens over her masked face, frantically trying to open her mouth…

Anna held her head still as she gave her her first bottle of food…

Placing her hands together in a gesture of prayer, Sue begged them to release her.

Anna just looked at Sharon.

“Awww… Isn’t she cute!”

“Yes… I think I’m going to keep her.”

“What about her boyfriend?”

“Oh… he moved on as soon as he heard she had been involved with the police. Seems the scandal was too much for him. Funnily enough, his family have paid for your services for the next year. They said making her ‘go away’ costs a lot less than the scandal would.”

“Oh! Really… did you hear that, Sue? You’re stuck like that for a year, at least.”

Sue just cried and wailed, shaking the bars of her playpen.

“Probably longer than that”, said Sharon, quietly, showing a darker side of her. “I always wanted a pet…”

Anna just raised an eyebrow.

“I do carry out dog-walking services as well”, she said.

Sharon chuckled. Sue screamed quietly into her gag…