The story is set in the distant future, where humanity is at war with Yuks , an alien life form which does not use mechanical spaceships nor constructions. Instead, it relies on life forms. The war has been going on for a long time, and humanity has not been able to come up with a solution against the life-form based ships and mines that the Yuks use. One day, a team of researchers led by Philip Kramer decide to build a spaceship which is powered by a human brain. They find the ideal candidate, Kramer’s old professor, a dying man who volunteers to donate his brain to the project. A human brain-controlled spacecraft would mean mechanical perfection. This was accomplished, and something unforeseen: a strange entity called … Mr. Spaceship!