The target in an infidelity case traveled out of town often for business. The private detective had a contract with an out-0f-state colleague to conduct surveillance on the target while he was out-of-town, (in the private investigators home town). After four nights of surveillance, the private detective had nothing showing infidelity, but something didn't feel quite right, you know that gut feeling.
The target left town and the private detective decided to review his surveillance video he had taken over the past few days. There were hours of video as he would follow the target from his business visits back to his hotel then sit and wait to see if he would re-emerge.
After reviewing the video completely through, something still did not seem quite right. He decided to watch the video's once more when he began to see a pattern. Target would arrive at the hotel, use the valet to park his rental car then go into the hotel. Over the four days of surveillance, the private detective noticed another man would exit the motel after his target arrived at the motel. He timed the appearances of the second man noted that were all within one hour of the the target's arrival. He also compared the height, weight, and build of the target to the second man. Primary difference? The second man had a beard.
You guessed it, being suspicious he was being surveilled, the target donned a disguise when he left the hotel. A few weeks later when the target returned, the private detective observed the "second man" emerge from the hotel an hour after the target arrived. He followed the second man and within a few blocks he emerged at another hotel with no beard. It was his target. He got great video of the man meeting a woman in the lobby of the second hotel.
Upon further investigation he found the man was renting two hotel rooms, changing in the first, putting on his disguise then traveling to the second hotel to meet.