Mark returns two years after Brothers in Arms to the Dendari Free Mercenary Fleet where he tricks Bel Thorne into taking him to rescue the clones on Jackson’s Whole. When they get there everything goes completely wrong. Miles, trying to save Mark, gets shot in the chest, cryofrozen, and lost. Mark has to figure out who he is when he isn’t trying to be Miles and he has to find Miles before anyone can try to make him the next Count Vorkosigan.
I love the character growth you get to see here for Mark. By the end of the book he is a very different character then at the beginning but every step along the way makes sense and grows smoothly.