the plot of mirror's edge follows faith, a member of a group called the runners. the runners deliver things from person to person as an underground system, as the city spies on the citizens a lot. faith's sister is accused of killing a candidate for mayor of the city, and faith finds out it's part of a plan to kill the runners. the true killer ends up being an ex-runner gone rogue working for the government, and faith saves her sister from being arrested.