Vivian knows that Hutch has a deep sleep and never wakes up at night and that Christians bedroom walls are soundproof.
What about the backyard?
It is a safe zone also, because Hutch never walks around, where he sits, he sits and never stands up until his wife or boss tells him to do so.
By the way it's common nowadays to let the wife sleep with the husbands boss inside his bedroom with the door closed while the husband sleeps in another room on a couch.
In this case, I don't see anything that points to cheating.
It's just an ordinary couple that got invited to a meal with an unexpected stay over.
The boss was worried about the couples safely return home at night.
The couple, especially the wife should be grateful that hubby has such a caring boss.