Sally is a natural Stepper and has a knowledge of where the soft places are. She is a legend in the stepping and combing community and is one of the pioneers of the Long Earth. The estranged daughter of the man who discovered how to Step and who invented the stepping box, circumstances force her to accompany him, and become somewhat reconciled with him, in The Long Mars. With Frank Wood to act as mediator, they explore several hundred thousand iterations of the planet Mars together, discovering, among other things, a race of sentient dinosaurs.
In The Long War, she acts as a ferocious advocate for the rights of trolls, regarding them much as Adora Belle Dearheart regards Golems, and is pretty much a non-smoking expy of Adora. She and Monica Jansson team up to rescue a troll jailed for seriously injuring a human, and set in motion the chain of events resulting in Joshua Valienté losing an arm as a trophy in The Game.