Plot summary
The Mirror Universe counterpart of Ezri Dax shows up at Quark's quarters on Deep Space Nine with a message: Zek went to the Mirror Universe in search of business opportunities and was kidnapped by the Alliance, who demand that Quark exchange a cloaking device —a device that can render a starship invisible—for Zek's freedom. Quark and Rom steal a cloaking device from the Klingon General Martok 's ship, which they hide by cloaking the device. They get the device to Ezri, and are forced to transport to the Mirror Universe with her when Martok discovers the theft.
Upon arriving at Terok Nor (the Mirror counterpart of Deep Space Nine), now under the control of the human rebellion against the Alliance, the three are arrested, since the Rebellion cannot allow the Alliance to gain such cloaking technology. They are rescued by Ezri's friend, the Mirror counterpart of Quark's rival Brunt. Brunt brings them to the Regent of the Alliance, the Mirror counterpart of Worf.
They learn that the mirror Kira Nerys—formerly the Alliance's brutal overseer of Terok Nor, now out of favor with the Alliance, and Ezri's lover—planned the entire affair; the Alliance never intended to release Zek. Brunt persuades Worf not to execute the Ferengi immediately, and Rom and Quark are imprisoned with Zek. Kira kills Brunt when he tries to convince her to release them. Ezri, disgusted by Kira's callous murder of her friend, turns against her.
Rom is forced to install the cloaking device on the Regent's ship, but despite his cooperation, he and Quark are still sentenced to die at the hands of Mirror Elim Garak. They distract Garak by comparing him to the Garak of their own universe, which delays him long enough for Ezri to arrive and inject him with the poison meant for the Ferengi.
Worf has the cloaking device activated, only to find that Rom has sabotaged the device to drain the ship's power. The powerless Alliance ship is easily overpowered by the Rebels' Defiant, forcing Worf to surrender to the Rebels. The Rebels bring the Ferengi back to Terok Nor, from which they can return to their own universe.
Credits
Adapted from Wikipedia contributors, The Emperor's New Cloak. Paragraphs and formatting adjusted; illustrations, reference markers, block quotations and non-story material omitted.