From the introduction:
Per Ardua is a Call of Cthulhu adventure set at a government research airbase in modern-day Britain. We’ve pulled this one from the back catalogue of past projects and as such it was written for 2nd Edition rules. Some conversion to later rules editions may be needed, but this should be fairly minimal (unless converting to play with d20 rules).
The text assumes a setting in the first decade of the 21st Century, with variations for a 1980s or 1990s setting given where necessary. The scenario features two main plots: one requires straightforward detective work to solve, the other a knowledge of the Mythos and/or some quick thinking in a crisis. As such this adventure can be tackled by quite a small party. It is best set in the summer months.