Bujold stretches her legs away from interstellar thrillers and into a little psychodrama. Miles' "evil" clone Mark is back, and he starts by borrowing the Dendarii Mercenaries for a mission to dispense some indiscriminate justice on the Jackson Whole clone-immortality business. The commando raid goes wrong, Miles' rescue mission goes even more wrong, and when the dust settles, Miles Vorkosigan is (mostly) dead and missing in action, and Mark has a lot of explaining to do to all the people that he's hurt.

The second act, on Barrayar, is some of the best stuff that I've seen from Bujold, as Mark tries to find his own identity while dealing with an alien culture, and come to terms with his parents Cordelia and Aral. Cordelia Vorkosigan is who author insert characters want to be when they grow up (in a good way). Lazarus Long and Jubal Harshaw are irritatingly smug pikers.

Unfortunately, the third act is not as strong. Mark embarks on a rescue mission to recover Miles-or his body. This goes poorly, and Mark is captured and tortured by a very unpleasant sadist. This isn't the first time that sex, torture, and violence has come up in the series, and like in Shards of Honor, I don't buy it as natural part of the story. Not to seriously analyze authors, but Bujold seems to like breaking her protagonists, and with Miles putting his life together, she needed to introduce Mark as New Xtreme Miles. I don't mind grimness where it fits: Reynold's Revelation Space has war criminals torturing each other against a backdrop of extinction machines wiping out humanity, and I love it. But somehow that sort of arbitrary sadism doesn't fit into the Vorkosigan universe.

In the middle of the book, Cordelia describes Miles as a knight-errant. The Vorkosigan books have a romantic heart. I guess the idea is to make dragons for our heroes to slay, but scarier than any dragon is a dedicated, resourceful, and dangerous human being with goals utterly opposed to your own. Miles Vorkosigan makes a great protagonist because of his energy, his ability to inspire, and his total disregard for the norms of civilized behavior when it suits him. For a book that plays with the idea of 'mirroring' as motif, Mirror Dance misses a chance to create an antagonist capable of looking back at our heroes.