The First Doctor, Steven, and Sara

Speaking of characters who didn’t have any room for their own story, Jean Marsh as Sara Kingdom shouldn’t have any space for added narrative, but “The Daleks’ Master Plan” specifically has a gap in the middle of it, and Jean Marsh seemed to enjoy doing Big Finish, so there’s more stories packed in there than you’d expect, some of which are quite good. Jean Marsh herself appears in most of them, which is only slightly unexpected, but pleasant. There’s a trilogy of Companion Chronicles in here that are all part of a connected story, but it’s the frame stories that follow release order, and the flashbacks take place in reverse order. If you’re doing this project yourself, I’ll strongly recommend that you break from the chronological order and listen in release order, just this once.