The Doctor has regenerated again, for a third time. His behaviour goes erratic and unpredictable due to this, so it's up to the investigation of Sarah Jane Smith, with the help of UNIT, to uncover the history behind the mysterious theft of plans for an incredibly powerful disintegrator gun. Sarah gets into the premises of Thinktank, a suspicious scientific research group with seeming ties to the theft, and after a fruitless visit to Professor Kettlewell, a former scientist at Thinktank and a specialist in robotics, she encounters the Robot, the creation that Kettlewell ordered the destruction of.
For the first episode I've watched of the classic Doctor Who series, it was pleasantly surprising to see the level of quality on display here. It has a simple but compelling premise, of the mysterious theft of top-secret UNIT documents, and is presented in a way dripfeeding the viewer the particular details of what happened, how it happened, who it was done by, and why it was done.
The effects do show its time, but they worked tremendously with what they could do, with fantastic kaleidoscope-esque point-of-view showings for the mysterious, unshown Robot building a great sense of unease.
Acting is superb, particularly the zany and erratic nature of the newly-regenerated Doctor being portrayed incredibly well by Tom Baker, who brings a very welcome display of charisma and energy to the role.
8.7/10, rounded up to 9/10 for the review :)