During the Dominion War, the Miradorn – ninety percent of whom are telepathically linked twins – allied themselves with the Dominion. Now, in the wake of the Alpha Quadrant's victory in that war, the Miradorn are eager to improve their relationship with the Federation – especially in light of the numerous dangerous devices the Dominion left behind.
One of them has killed a Miradorn scientist named Or-Lin. Now, the S.C.E. team on the U.S.S. da Vinci must deactivate the rest of the devices before they become responsible for wiping out the entire Miradorn species – but the only one who can help them is Or-Lin's twin, Em-Lin, who is still devastated by the death of her sister…