What do you mean by a summary? Or, a better question might be where are you up to? The first five chapters basically map out the differences in this AU part of S7, from Spike in the Initiative through to when Buffy comes back from the Shadowmen, which is when things go fully AU (with the story from there told in the scenes at the start of each chapter). Then things progress. I've slightly always hated using headers, but I might have missed something in my opening ramble - is there a bit of info you were looking for specifically?