See Mark try and fail to cheat on her

When Cynthia and Mark arrive at Darren and Jade's house on Sunday, Cynthia has a platter of Caprese salad in her hand and her phone in her pocket, ready to humiliate her husband. There are quite a few people there, most of them friends they'd known for a long time but a few people who Darren and Jade knew independently of them. It was enough people that if Mark and Vanessa wanted to sneak off into one of the many rooms in Darren and Jade's house and fuck, their absence would likely go unnoticed, as would Cynthia's absence if she followed them. Vanessa was already there, and Cynthia was able to greet her convincingly enough as to not hint at what she knew in the slightest. Still, she couldn't help but notice how Mark's hands lingered on Vanessa's hips when she greeted him by kissing his cheeks.

Vanessa went through the motions of having fun at the pool party - swimming, conversation, receiving compliments on the Caprese salad - while keeping an eye on the two of them from afar. Occasionally, she'd return to her phone and increase Mark's horniness. She could see the glances between them, feel the sexual tension. Finally, as the sun is setting and the party is migrating from the pool to the fire pit, she sees Mark touch Vanessa's arm and whisper something in her ear. Then he heads into the house, and after waiting a few moments, seemingly to appear inconspicuous, Vanessa follows.

Cynthia moves cautiously through the house, not knowing which of the rooms Mark and Vanessa are in.
When she hears their voices coming from behind one of the doors, she grins. Cynthia happens to know that due to a quirk of the house, everything said in that room can be heard, crystal-clear, from a vent in the ensuite of the next room over. She creeps into that bathroom and sits on the floor. She can hear them softly moaning into each others mouths as she opens the iCock app.