The Ark

So after the historical adventures of "The Massacre" and the introduction of new companion Dodo, the TARDIS lands on a spaceship taking the last survivors of Earth to a new planet, along with the Monoids, a race of cyclops who are much more intelligent than they look.

The story is split into two sections which is pretty interesting: the first is about Dodo giving a cold to all the people onboard the Ark, which the Doctor then cures, and the second deals with the Ark at the end of it's voyage and the Monoids' enslavement of the remaining humans.

In the first half of the story, you feel sorry for the Monoids and the humans are the villains, and this concept is reversed for the second part of this serial, which shows the good and bad sides of all races. The climactic battle is interesting, and the final scene of the Doctor disappearing links in with the next serial: "The Celestial Toymaker".