What is the subplot of a sound of thunder by Ray Bradbury?

The subplot of "A Sound of Thunder" involves the consequences of time travel and the impact of altering the past on the present and future. As the characters in the story travel back in time to hunt dinosaurs, a seemingly small alteration in the past has significant ripple effects on their return to the present. This subplot underscores the theme of the fragility of time and the potential risks of tampering with it.