Try to react to everything that's happened with dignity. Do not stoop to scandals, accusations and statements about "meaningless lost past." Yes, you love your wife and I don't even think about cheating, and she came to you deceitfully – consciously and without any mercy. But the fact remains that she slept with another. No matter how you treated it, don't let her humiliate you even more. Quietly put it on notice about what you know about her adventures with the truth. On the assurances of "it all happened by chance", "I didn't realise" do not pay attention. Time she at least tried to hide the fact of change from you, so knew what they were doing, and knew perfectly well – but for now just trying to find some excuse.
Don't try to find out as much information as possible about her lover. Why do you need it? Easier by the fact that you will know his phone number, car, place of residence and work address, you still will not. And if you try to call him or look for him again in any way possible, he will tell your wife about this – and together they will laugh at you. So it doesn't matter who seduced your wife – I mean, it's not only a lover, but she is.
Will have to decide what to do next. Awareness of their future in a similar situation – a very serious step. Are you willing to put up with the betrayal of a loved one? Will be able to live with his wife under the same roof as before? If not – continue a pointless relationship is not worth it. If you are willing to close an eye on her "gaffes" in the name of love, children or anything else – you know, even if the cheating will not happen again, to regain the trust and mutual respect will be very difficult. To return to the family love and to forgive, have to visit a psychologist or therapist.