Upon returning from an intergalactic mission, the Crystal Gems—Garnet, Amethyst, and Pearl—have brought a mysterious magical hourglass. Steven Universe, the youngest member of the Crystal Gems, gets his hands on the device and discovers that it has the ability to let him travel back in time in order to make snappy comebacks. However, his actions soon bring about a deadly adversary, with everyone's lives dependent on Steven being able to make a worthwhile comeback.

When a menacing red eye is about to hit Beach City, the only thing that can destroy it is a Laser Light Cannon which once belonged to Steven's mother, Rose Quartz. Thus, Steven enlists the help of his father, Greg, and they search through his storage for the cannon.