The first rule of time travel is to never change anything. Otherwise, the resulting “butterfly effects” can ripple through time and wreak untold havoc on the unwritten future. But on his last test as a Space Time Agent, Valerian messes up. Not only does he save someone who would have been killed, but he’d have died himself if she hadn’t rescued him! As a result, nothing in the future is where he left it, including the Earth!