Gribbin presents the recent dramatic improvements in experimental techniques that have enabled physicists to formulate and test new theories about the nature of light. He describes these theories not in terms of hard-to-imagine entities like spinning subnuclear particles, but in terms of the fate of two small cats separated at a tender age and carried to opposite sides of the universe. In this way Gribbin introduces the reader to such new developments as quantum cryptography, in which codes that are permanently unbreakable can be made using quantum effects. He goes on to possible future developments, such as the idea that the "entanglement" of quantum particles could be a way to build a teleportation machine - "beam me up Scotty" could really happen.