Katherine Harmon Courage dives into the mystifying underwater world of the octopus and reports on her research around the world. She reveals, for instance, that the oldest known octopus lived before the first dinosaurs; that two thirds of an octopus’s brain capacity is spread throughout its arms, meaning each literally has a mind of its own; and that it can change colors within milliseconds to camouflage itself, yet appears to be colorblind.