 The Enterprise is in a remote section of the galaxy on a mission of star charting when they pick up mysterious radio emissions. While investigating they find themselves picking up speed. As they gain momentum they are being drawn towards a strange, dead star. They achieve orbit and discover an alien starship is also in orbit around the star. While investigating they discover that the ship has been badly damaged and is over 300 million years old. When they beam back they unknowingly bring back a malevolent energy source which attempts to take over Enterprise.