Down There: Cuckolded by the Old Man

Trisha and Colin are a typical couple whose lives have gotten more than a little stale. To spice things up in the bedroom, they look for a No-Strings-Attached relationship to bring another man in the bedroom. That's when they meet Nick. Nick is an old man, living out his retirement in Europe. What Colin doesn't realize is that the older Nick wants to have Trisha all to himself, and relegate him to the role of humiliated cuckold husband!

Here's a taste:
"A week later, during which time Tricia had been brought to fever pitch via Skype and email, Nick was up early to catch the 8 a.m. train to Castelo Branco, Trisha and Colin’s nearest station. He arrived shortly after eleven and was met by Trisha, as previously agreed. On the ten-kilometer drive to the farm, they passed through a wooded area. Nick told her to pull off the road into a suitably secluded area.
As soon as she turned the ignition off, he leant over and kissed her."