Until the Dominion War, the pre-warp civilization on Coroticus III was under observation by the Federation – and then the Dominion moved in. Forced to abandon the planet – and leave a person behind – Starfleet does not return until after the war is over and the Dominion has pulled out. Carol Abramowitz and a team from the da Vinci must now determine the extent to which the Dominion contaminated Corotican culture – but that's the least of the S.C.E.'s problems, as they uncover a mass-murderer, who may be the Starfleet officer left behind…