Talk about it here.
Having promised her father, an old friend, the Doctor takes Milena for a trip in the TARDIS. The ship lands and she believes it's her own world, Xenon, but the Doctor thinks the Time Lords might have put them elsewhere. They appear to be on an asteroid, several miles wide, on the outskirts of Xenon's solar system. Milena asks to explore, and they put on oxygen suits. While the Doctor notes the rock appears to be cooled lava, Milena falls and breaks her oxya-suit, almost suffering from oxygen starvation before the Doctor hurries her back to the TARDIS.
He resets the time co-ordinates for Xenon; the Doctor theorises about the formation of the asteroid from a larger body like a star when Milena speaks with another voice. Her eyes are vacant, her body glowing with a pale-green light. "We are Zicons," the voice says. Milena moves to the controls; the Doctor grabs her, but her skin is burning hot and she knocks him back. The Zicons, appearing as particles of light of every colour, demand his obedience or his companion will die.
They set the TARDIS on course for their star Migron. They feed on incalculable heat and became trapped when the asteroid was thrown off. As the ship becomes hotter, the Doctor protests but they attack his mind. He aims a thermo-condenser at them, saying he can drop the temperature to zero. They mean him no harm, but he gives them five seconds to prove it. With no choice, the Zicons leave the ship and the Doctor quickly sets the controls in reverse, knocking him and the freed Milena unconscious. On the star, the Zicons return home.
Millions of miles away, Milena is returned to Xenon — though she has no memory of what happened — and the TARDIS departs. Approaching Earth, the Doctor muses that some aliens are so gullible; the thermo-condenser was really a solar compass. Now above the Earth, the Doctor hopes for a better landing, but wouldn't mind if he "splashed down in the sea!"
- Milena has longed to travel through time and space with the Doctor.
- Seeing strange, blinding lights is the effect of oxygen starvation.
- The Doctor has a couch in the TARDIS.
- Migron is hotter than Sol.
- Milena is from Xenon. She is travelling with the Doctor as a favour to her father. She is explicitly referred to as the Doctor's "companion".
- This story originally had no title and is given this for the sake of convenience. It is only called "Dr Who."
- While from Xenon, Milena is called a Zenonian. Xenon happens to be the same planet that Frobisher would later be said to be native to.
- The Doctor is referred to both as the Doctor and as "Doctor Who", while TARDIS is spelled "Tardis".