I think I'll never employ a private investigator, but you never know!
I've never had any experience with a private investigator but a friend of mine was involved in a problem. She had an affaire with a married man who worked with her at the same hospital. They used to meet twice a week at my friend's home. They used to spend all the night there and then went to work together. He's a doctor so he used to say to her wife that he was going to work overtime (during all the night). Of course he dind't go to the hospital but he paid someone else for doing his job and he went with my friend. His wife who wasn't stupid didn't think she had a very responsible man working day and night, so she decided to employ a private investigator to know exactly what was going on there! She discovered her housband was very "busy" but not at hospital and she decided to send him a letter because she wanted to divorce him. Well, my friend and this man are living together, but I'm not sure he's not doing the same to her!