The Harbinger is a d20 System scenario for 9th- to 11th-level characters. Part of AEG's Adventure Keep line of short, cheap modules in half-sized format (4-1/4"x11"), it is intended to be run as a single session. Intended for use with the Dragons sourcebook. From the back cover:

The most dangerous foe is the enemy you once called friend...

The small peaceful town of Brookvale lies in the sheltered forest curve of a wide river, protected from weather by the sweeping arms of massive elm trees. The town boasts a library, a cultural museum filled with historical exhibits, and the temple of Ghesse, the River-goddess. Over the mossy gate hangs the sign of the Royal Testament — the King's own favor. It is a gentle place, where goodly folk spend time in craft-halls and educating themselves through study. Under the watchful eye of an old wizard named Calendrus, the town has prospered and grown. Until now...

A dragon appeared within the forest, recently, ravaging outlying villages and destroying everything in its path. It shows no mercy, nor any interest in peace — it exists merely to kill and maim. Yet the marauding dragon's hide shines silver in the sunlight — a color that should stand for goodness and justice. Something must be terribly wrong to drive a good dragon to slaughter innocent peasantry... and the dragon is headed directly for Brookvale!