During the Cell Saga of Dragon Ball Z, Vegeta and Trunks entered The Time Chamber/The Room of Spirit and Time. This story begins there, just with a little twist: What If Vegeta and Trunks were trapped in The Time Chamber? Yes, I know, there are many vidoes on YouTube following this exact story, but this is fun because you can only somewhat control the outcome. You're supposed to be Vegeta by the way.