In the 42nd Century a secret agency is formed and tasked with sending highly trained assassins through time. Their targets are chosen so that their deaths alter aspects of the timeline in an attempt to avoid major catastrophes.
These Time Assassins work alone, slipping from one destination to another, rarely ever returning to their period of origin. Without backup or support from the Agency, Assassins must survive however they can, often having to repair gear or replace clothes with whatever they can find in the era they are in. As a result, they often look completely mismatched, with styles and technology from both past and future civilisations.