We have a persistent brick wall on my family's Gardner line, back in Scotland. It's bugged me for years and years. I'm attempting to learn more about the area and the people around my ancestors, in an effort to find where they disappeared to in the preceding generations. So. I'm told this is called FAN club research. Here's an introduction.
I also located some Family Search pages about the areas these people are from. I know of records that were made in Falkirk, Stirlingshire, Scotland, as well as several parishes in Renfrewshire, Scotland. I've started making a list of all the locations they were in, and after watching the FAN Club video, I will probably move this to a spreadsheet, the more easily to organize and search as I widen my net.
Gonna be an adventure!