The Twin Dilemma

STORYLINE

Is the Doctor really losing his mind? After his fifth regeneration his behavior certainly seems to point that way.

Having tried to strangle Peri, he's landed the TARDIS on the asteroid Titan 3 determined to pursue the quiet life of a hermit. But the giant dome on the horizon seems set to shatter his piece.

Just who are its mysterious inhabitants? What is their connection to the kidnapping of the twins Romulus and Remus, famed for their mathematical genius? And where are the giant Gastropods?