Nervous confusion.

"...um, honey. What's...going on?"

"I'm just doing what she wanted. This was her idea.
She wanted to surprise you."

While your Wife trusts you- enough to not freak out when she finds her Stepsister tied and gagged naked in the Living Room-, she has questions.

You 'explain' that she wanted to surprise you with her being tied up and joining her in her fun.
She knew about what she did with you, after seeing some pictures on her phone.

She blushes, realizing that she did have some pictures there.

To seal the deal, you show some messages from her that you faked.

Using a digital copy of her phone, you 'sent' texts to you asking you to do what you said.

"I...I had no idea she wanted to do that."
"You want to play with her?"
"I mean...if she's into it...sure."
"Gag time then, honey."

She smiles and then lets you give her a matching blue tape gag.
More rope goes on her, giving her a matching harness to Emily's.

You wait a moment and then fondle Emily's tits, alongside Veronica's.

This stirs the former awake and she's confused- to say the least.
She looks down to see herself naked.
She feels the ropes holding her in place.
She looks at her Stepsister in matching naked bondage and doesn't know what to do.

Emily looks at you and Veronic joins her 'playing along.'

"Oh good- you're up. Let's have some fun, shall we?"