There is an extremely high chance that your wife is cheating on you. Coz something similar happens to a close friend of mine. The wife would tell him, i want freedom and go to have some fun. And she also went out with other guys alone. In the end, it was found out that she was cheating on me friend.
One more thing to add, according to the eyes of the law. A married woman is not allowed to go out alone with the opposite sex. That constitutes to unreasonable behaviour.
PS : If you want to know the truth, spend some $$$ and hire a PI. The truth will then be revealed.
