A spaceship from a previously unknown planet lands in the Scottish moors, bringing a humanoid alien to Earth near the observatory of Professor Elliot (Raymond Bond), just days before the mysterious Planet X will pass closest to our planet. When the professor and his friend, American reporter John Lawrence (Robert Clarke), discover the spaceman, they help it when it is in distress and try to communicate with it, failing in their attempt. They leave, and the alien follows them. A colleague of the professor, the unscrupulous and ambitious scientist Dr. Mears (William Schallert), discovers that the humanoid speaks in musical tones and tries to force from it the metal formula for its spaceship. He shuts off its breathing apparatus and leaves the spaceman for dead, telling the professor that communication was hopeless.