The writing of City of Death was credited to the fictional David Agnew, but was mostly the work of the late Douglas Adams.
First broadcast during 1979 the story featured Tom Baker as the Fourth Doctor alongside the Second Romana played by Laila Ward. The Doctor and Romana by coincidence are taking a short break break in Paris, when they become aware of someone messing about with time travel. At that point they are in the Louvre looking at the Mona Lisa.
They soon learn that it is Sardoth who is attempting to make a time machine in order to save his alien race the Jagaroth, who were killed in an explosion 400,000,000 years ago that had brought live to planet Earth. You will know he is the bad guy, Julian Glover always plays the villain.
This is one of the funniest Doctor Who stories ever, as the Doctor and Romana literally run around Paris in order to stop the plans of the Sardoth. The Doctor even goes back to Florence in the TARDIS to write ‘fake’ on the extra copies of the Mona Lisa Sardoth had forced Leonardo Da Vinci to paint for him.
Over all this is a great adventure, and watch out for a cameo appearance from John Clease as an art critic baffled by the TARDIS.