It's a textual adventure (some graphic embellish it, but is purely decorative and has no role in the game).
You give commands usually composed by a verb plus a noun (e.g. "go north", "examine desk", "drink potion") and are told what happens ("you cannot go in that direction", "there is a pen on the desk", "you feel reinvigorated"). You have to explore the locations, collect items, use them when appropriate and in general imagine how to overcome the various problems in order to accomplish the final goal of the adventure.
You are Amos Newton, young assistant of a scientist in modern days. Using a device of unknown origin, your mind has been transferred into the body of an alien being living on a different planet in future times. Such planet is going to be invaded by humans who kidnapped the alien to study him. Controlling the body of your host, you were able to escape and reach his spaceship. Unfortunately, it was sabotaged and instead of the intended destination, it flies towards a giant orbitant spaceship of the humans.
You will have to continue to control the body of your host to inflitrate the enemy spaceship, use their computer to repair yours and finally escape.