Review for all 3 episodes:
This story from writer Louis Marks is rather like a 50s sci-fi movie and is fun, interesting and impressive in the first two parts before falling a bit flat in the third episode. It has very good effects for its time especially considering the low budget.
The TARDIS and its crew get miniaturised due to a strange side effect of the TARDIS doors opening before materialisation. It leaves them in a contemporary Earth setting but tiny (about an inch tall) making the normal world into an alien one. There is also a sub plot about the development of a dangerous pesticide and gangster like efforts to bring it to market despite its deadly side effects.
All this is a very interesting idea, the main cast and script are good and the first two episodes are well executed apart from one improbable moment when they stumble upon some giant ant eggs which they clearly would have seen before they fall over them. This was a problem caused by the small size of the set and is pretty forgivable.
These first two episodes are entertaining and impressive overall, it is the last part with its slightly jumbled and unsatisfactory conclusions which rather let it down. However, this final episode is still not bad at all and the overall story is good fun and a good adventure if not top quality for the series.
This really shows the inventive, ambitious ingenuity of early Doctor Who.
My Ratings: Episode 1 - 8.5, Episode 2 - 9, Episode 3 - 7.5
Average rating: 8.33/10.