Wife cheated? How can I ask my wife if she had sex?

by Ken
(Texas)

My wife and her sister and husband went out one evening. My self and brother in law got drunk and I was dropped off at home.

The women went to a bar and picked up two men and went for a ride in the car. The sister has had an affair with this man many times. Do you think my wife had sex with this other man? I know her sister did. How can I ask my wife if she had sex?