From the file's introduction
No one in the modern world is well trained or well guarded enough to be completely impervious to harm. Despite the best and most modern safety measures, heads of state are still assassinated, rich and powerful individuals are still kidnapped and ransomed, the most valiant heroes still fall in battle, and terrorist attacks still take the lives of innocent victims. Life is fragile, and no matter how carefully it is guarded, some way always exists for a sufficiently fanatical opponent to end it.
Nevertheless, a certain haughtiness comes with experience. Typically, heroes who have defeated numerous threats to themselves, their loved ones, and their ways of life develop a certain pride in their ability to overcome the dangers of the world. All too often, however, this pride spills into overconfidence.
A Friendly Warning explores what happens when such experienced heroes become the targets of a man bent on proving that they are still vulnerable. This adventure can be set in any locale, but the best choice is a place in which the heroes feel safe and secure. The antagonist, Remi Leone, is stalking the heroes on their home ground, trying to get the better of them despite the fact that they have every possible advantage at their disposal.
A Short d20 Modern Adventure for Four 18th-Level Characters