Head back down.

You leave her on the bed and head back down to the dining room, where your wife and Steven remain none the wiser. You continue to screw around with the smartphone app, no doubt blasting a few more orgasms through Gemma upstairs, and you swear that you can faintly hear a scream or two through the noise of the music and chatter at the dining table. It's a bit disappointing you can't join in, but tormenting her gives you some pleasure all the same. Soon the meal is finished and you begin to clear the table, while your wife heads upstairs to check on Gemma. You remember to discreetly switch off the vibrator using the app in case your wife hears it. She returns not long after, with a look of concern on her face.

"Gemma looks horrible," she says to Steven, "She's absolutely drenched in sweat."

"Maybe let her just rest here for the night," you suggest, "She might feel better in the morning. I can drive her home."

Steve is appreciative of your 'hospitality', and the three of you enjoy some drinks in the lounge room before he heads home. Your wife provides Gemma with a spare set of nightclothes and a robe, and given how late it has become, the two of you head to bed.