And here we are with the fourth Doctor. Tom Baker has always been regarded as the ultimate Doctor, and he kept the role for the most long time ever, seven seasons.
In a certain way, this is a rather unusual story for the fourth Doctor. In fact it is a UNIT story, where the Doctor is still UNIT's scientific advisor.
UNIT stories were typical of the previous Doctor, Jon Pertwee: the Doctor was exiled on Earth by the Time Lords, and could not use the TARDIS, if not occasionally. Then UNIT stories became ripetitive, and the Doctor regained the use of the TARDIS at the beginning of Pertwee's fourth season. Pertwee liked UNIT stories very much, and also for this reason decided to leave.
Anyway, for a question of continuity, it seemed a good idea to have a UNIT story to introduce the fourth Doctor. There would have been just two more in the following season, then no more until 1989, showing a retired Brigadier...
Being his very first appearence as the Doctor, Tom Baker is overplaying a little, needing more confidence with the charachter. No worry about that: we know how he went on.
Now the story. Back from the voyage on Metebelis III, the Doctor regenerates.
Meanwhile, a mysterious (and apparently superhuman) thief steals the plans and the components for a new disintegrator gun.
As soon as he recovers, the Doctor traces the crime to a group of scientist called Thinktank, and to a robot designed by Professor Kettlewell, a former member of that group...
Enjoy!

WARNING: to read the comic you need Acrobat Reader.

ROBOT part I - part II - part III - part IV