Mirror Dance is a Hugo- and Locus-award-winning science fiction novel by Lois McMaster Bujold. Part of the Vorkosigan Saga, it was first published by Baen Books in March 1994, and is included in the 2002 omnibus Miles Errant.
Mark, Miles Vorkosigan's clone, masquerades as him and dupes his mercenary force, the Dendarii, into undertaking a mission to free clones held "prisoner" on Jackson's Whole, an anything-goes freebooters' planet where Mark was created and raised. These teenage clones are scheduled to have their brains replaced by those of their wealthy, aged progenitors. When Miles finds out, he attempts to rescue his troops and his brother from the mess Mark has made, but is killed by a needle-grenade. He is frozen in a cryonic chamber on the spot, but the medic in charge becomes separated from the rest of the men while retreating under fire. The medic uses an automated shipping system to send the chamber to safety, but is killed before he can tell anyone what he did and where he sent it.
The Dendarii flee the debacle and take Mark to Miles's parents on Barrayar. Cordelia accepts him as another son and has him acknowledged legally as a member of the family. After a while, Mark is convinced that Miles is still on Jackson's Whole, and decides to go there himself to look for him, since Barrayaran Imperial Security does not believe him. Cordelia helps by buying him a ship.
Meanwhile, the frozen Miles has been resuscitated by the Duronas, a research group cloned from a medical genius and employed by Jackson's Whole magnate Baron Fell. They hope to engage the services of the Dendarii, who have a reputation for difficult extractions, to help them escape from Jackson's Hole. Miles' memory takes some time to return, and the doctors treating him do not know whether he is Mark, Miles or Admiral Naismith (Miles' cover identity as the commander of the Dendarii).
Mark finds Miles, but is captured by Miles' old nemesis, Baron Ryoval, and tortured for five days, His personality fragments into four sub-personalities: Gorge the glutton, Grunt the sex pervert, Howl the masochist, and Killer the assassin. Together, the first three protect Mark's fragile persona, while Killer bides his time. When Ryoval's assistant informs him that Mark seems to have adjusted remarkably quickly and is actually enjoying the torture, a frustrated Ryoval decides to study his victim alone. Killer takes the opportunity to kill Ryoval, enabling Mark to escape. Mark sells Ryoval's security access codes to Baron Fell for a large sum of money and the Durona Group.
Miles' short death and revivification have serious repercussions for his health. Mark has his own problems, thanks to his strange upbringing, complicated by the torture. When he asks his mother for help, she sends him to Beta Colony for psychiatric treatment and therapy.
By necessity, this novel is told from the viewpoints of Miles and Mark. This was the first novel in the Vorkosigan series to be written this way, though not the first time Bujold has employed this style; the first occasion was in Falling Free.
Mirror Dance won both the Hugo Award for Best Novel and the Locus Award for Best Science Fiction Novel in 1995.