"...Had it not been you, there would have been other
travellers drawn into Mandragora's Helix.
Earth had to be possessed and checked.
Man's curiosity might lead him away from this planet until,
ultimately, the galaxy itself might not contain him..."
STORY PLOTLINE
The TARDIS is temporarily captured by the Mandragora Helix, a spiral of energy with a controlling influence, at the centre of which the ship is infiltrated by a sparkling ball of energy.
