'The War Machines' is a story that, when broadcast, signalled a change in direction for Doctor Who. It is adapted here by its original author, Ian Stuart Black.
The Doctor and Dodo arrive in London, where the Doctor senses evil in the Post Office Tower. Trading on the name of former companion (and now computer expert) Ian Chesterton to gain access to gain access to what turns out to be the base for the super computer, WOTAN. It is intended to link all computers in the world are linked via WOTAN (which means the Internet would have been invented in 1966!). However, it turns out that WOTAN has plans of its own...
The first televised Doctor Who story to be set in its entirety on contemporary Earth, the story is essentially the template for many future stories - particularly the beginning of the Third (Jon Pertwee) Doctor's era.
It also sees substantial changes to the TARDIS crew. Dodo is back on Earth in her own time, and is obliged to leave during the course of the story. More importantly, new companions Ben and Polly are introduced. They don't follow the templates set by original companions Ian and Susan, and represent a new kind of companion who would be generally replicated over the next five years.
Those are the good points. The story itself is not very original, and the adaptation is quite straightforward. Worth a read (or a watch, the video is available) for Doctor Who fans, but probably enjoyable to more casual readers as well.