What is the cheapest and easiest way to catch a cheating spouse in the act?

I need to find either strong evidence or indisputable proof that my wife is having an affair.

I am certain that she is, but I can’t prove it yet. What is the cheapest and easiest way to catch a cheating spouse in the act?

Tags: Act, Afair, Cheating Spouse, Having An Affair, Indisputable Proof