Tom Swift Jr. works with the Navy to recover a Jupiter probe missile designed and built by Swift Enterprises on behalf of the government. However the Brungarians intercept the probe -- and Tom must race against time to recover it from the bottom of the ocean before the Brungarians can steal the probe and its scientific data. As the story unfolds, Tom invents several underwater devices to assist with the recovery and counter the threat of a new stealth submarine developed by the Brungarians.