I was... bored?
The episode is long ! (All 4 episodes, then...)
The first one is really good. We discover the universe in the skin of the 2 "protagonists", namely the two teachers of the Coal Hill school, Barbara Wright and Ian Chesterton, whose actor William RUSSEL is now deceased.
But the rest is passable, even downright bad!
The whole story about "yes blah blah blah fire is so good" well it could have been resolved in 2 seconds !
Spoiler: the Doctor makes fire, Barbara and Ian realize that it's true, that they are traveling in time for real, and BAM! End of the story. In short, if you want a quality episode of DW, don't start with this one. Rating of 4/10 so 2/5.