He humiliates them.

"Tops off. Now."
He strongly emphasizes that last word.

They gulp, share a look and take off their tops.

It's not like he didn't see their tits already.

He ties the taller one- Randy- up first, making her watch as he gives the other one- Chanel- 'the works.'

She's tied to the stairs and gagged tightly, rope around her now-free tits.

He soon ties Randy the same way and they struggle in vain.

https://imagecdn.clips4sale.com/accounts99/116614/clips_previews/prev_28291215.mp4

He leaves to prepare things.

Little do they know that this is being filmed though.
Heh heh.

When he returns, he catches them AGAIN trying to get each other loose.

"You never learn..."

He grabs some scissors and cuts their skirts off, ruining the garments and leaving a pile of scraps.

He pulls their panties down to their ankles, warning them that another attempt will make them lose those permanently.
They nod.

As he leaves, the now naked duo shivers in fear.

He's getting lots of good footage as he waits to hear from the gang.