"KEEP THE STARS FREE" - That's the motto of the Galactic Security Service. Using vast ships and the massive weight of Federation diplomacy, it sweeps the star-ways to hold inter-stellar conflict in check. Most of the time.
The Federation fleet is big enough for most missions. But for some it's too big, like when a dictator's throat needs cutting. Or a spy lost in a prison colony on Golot 4. Dirty Jobs. Violent jobs. Lonely jobs. That's when they send for SIMON RACK.