In a high-tech lab, a team of scientists creates a groundbreaking time machine integrated into a watch and a serum for time travel. Seven volunteers are selected for the first human trial, but a critical error leaves them with only one return serum. The group is split: two, Dr. Amelia Hughes and Dr. Robert Quinn, are sent to the prehistoric past, and the remaining five to an unknown future.

In the past, Amelia and Robert face immediate danger from dinosaurs and struggle to survive. They forage for food, build tools, and encounter both hostile and benign prehistoric creatures. While searching for food, they discover a cave with ancient drawings and stumble upon an advanced underground civilization powered by a colossal energy nucleus and led by a meditative king.

The ancient inhabitants, perceiving them as a threat, chase Amelia and Robert.

Will they be able to deal with them? How will they return to the present? Read the book to get the answers to all alike questions.