"The Space Museum", Part 4

As the episode opens, we find that Ian has fund the Doctor in the midst of being processed into a display.  He is told that the Doctor is "as good as dead".  Then we find Vicki aiding the rebels in starting their revolution.  She returns to the Museum accompanied by one of the rebels, and Barbara comes to in the midst of the gas.  The Doctor comes to after the processing was reversed, and he claims he understands what is going on, and he and Ian are recaptured.  Barbara leaves the museum and is captured, but quickly rescued by Vicki, only for the two of them to be recaptured.  The companions discussed whether or not their actions have been enough to change the future and the Zeron rebellion manages to free them, and the Doctor remarks that the future doesn't look too bad at all.  The Doctor took a souvenir of the museum ... a time and space visualizer and Vicki departs reluctantly.  The episode ends with a Dalek reporting the movements of the TARDIS ....