Sisko is abducted by a double of O'Brien, who takes him to the mirror universe that Kira and Bashir visited a year ago. This O'Brien explains that Sisko's counterpart, the leader of the Terran rebellion against the Klingon/Cardassian Alliance, has been killed. O'Brien wants Sisko to pose as his dead double and convince a Terran scientist with the Alliance to join the rebels. That scientist is Jennifer Sisko, the counterpart of Sisko's late wife. Since she is building a device that will betray the secret location of the rebels, Sisko must convince her to join them before she completes her work or the rebels will have to kill her. Unwilling to watch Jennifer die again, Sisko agrees to intervene. He meets the rebel counterparts of Bashir, Rom, Tuvok from the starship Voyager, and also Dax, who is Sisko's mistress in this universe. Only O'Brien knows that Sisko is an impostor.
