System Shock is an original novel written by Justin Richards and based on the long-running British science fiction television series Doctor Who.

It features the Fourth Doctor, Sarah and Harry and is followed by the BBC Books Past Doctor Adventures novel Millennium Shock, also by Richards.

However, mysterious events are plaguing London.

The Doctor receives a computer disc from a dead man.

And to top it all off, it seems that an alien race is planning a takeover using Earth's ever expanding computer technology.