An Abrupt End
When two people are matched, they do not always find each other attractive. It can be even worse if they are on a date with another couple, and there might be an abrupt end to the date if things go wrong. While they might have had the best intentions, the couple must realize their friends are not always suitable for each other. It can turn their evening of fun into a nightmare for all of them.
The problem often begins when they introduce the two, and it can be a polite but distant meeting. Détente can be easier between countries with a long history of warfare, so expecting two people who have been pushed into being together to get along can be an issue from the start. As long as all of them understand they must only get through the evening, it can be a wonderful time for the four of them to just have a relaxing night on the town.