The tracking theory treats knowledge as counterfactual covariation of belief and truth through a sphere of possibilities. I argue that the tracking theory cannot respect perceptual knowledge, because perceptual belief covaries with truth through a discontinuous scatter of possibilities. Perceptual knowledge is subject to inner derailing: there is an inner hollow of perceptual incompetence through which the differences are too small to track. Perceptual knowledge is subject to outer derailing: there are outlying islands of perceptual competence that extend well past skeptical sinkholes.