After losing their parents in a horrible car accident, fifth-grader West and his genius third-grade sister, Gina, try to cope with the enormous change in their lives. While digging around in their father's shed one day, they find some old boxes with the word "NASA" printed on them. One large box contains their father's unfinished motorcycle, and in a tribute to their dad, the children decide to finish building it.

They also discover a top-secret file containing abandoned blueprints for a tiny, silver box that allows people to travel through time. When Gina corrects the scientist's miscalculations, she finishes building the time machine and tapes it to the motorcycle. Suddenly, West and Gina are propelled into the past where they meet Albert Einstein.

With Einstein's help, West and Gina travel to the future and discover the city of Atlantis. But when they try to travel back to the day before their parents were killed, the time machine malfunctions, and they arrive on the exact day of the accident. Time is running out, but the Atlantians may have a way to help save West and Gina's parents .