Grim Frequencies is a series of adventures for d20 Modern, all started by similar bizarre transmissions. Each short adventure can be dropped into an existing campaign easily. While each adventure will be for increasingly higher-level heroes, none of them provide enough experience points to advance the heroes. Instead, the main action of the campaign
should advance the heroes with these missions providing brief interludes.
Each adventure puts the heroes in increasingly complex moral conflicts, and ultimately asks whether the ends justify the means.