In 2320, Captain Ulysses Grant of the United Space Corps, his ship, and all its crew have ysteriously disappeared somewhere on the Galactic Rim. His children, Penelope, Buster (the ten year-old), and their grandfather, Cyrus Grant, trick a reluctant warrior, who happens to be a Prince of the Space Otters, into helping them find their father ... and many adventures along the way.
For 200 years, humans have explored and mapped the galaxy in ships operated by the United Space Corp. Forty years earlier, earth narrowly escaped destruction at the claws of a race of giant insects, the Arcturians, commanded by the dreaded Galactic Overlord, a mysterious entity whom no human has ever seen.
One year ago, Captain Ulysses Grant of the Space Corp went to investigate strange bursts of energy at the galactic rim, and he and
his crew are declared missing in action. Captain Grant's children, Penelope, 15, and Buster, 11, who now live with their grandfather, Cyrus Grant, are determined continue the search that is all but abandoned by the Space Corp.
They encounter a six-foot tall otter, Nurfel, who gives them a special map that might lead them to their father. They, along with their grandfather, who seems to mysteriously know Nurfel and how to speak to him in his own language, follow Nurfel to his giant space ship, the Abalone, hidden in the asteroid belt and ask for his help in finding their father. Nerful has his own agenda, but they manage to coerce him
and begin a series of adventures that ultimately ends in a showdown with the fearsome Overlord.