The final 20 mins should've been the whole movie...
I'm sure a lot of people think otherwise but I'm not very fond of the first 3/4. IMO it's just an overlong exposition with lots of scenes that don't really add to the movie. Just take that superfluous appearance of Christopher Lee. Totally unnecessary for the movie's narrative. Sure, the police chief was fun, but all we needed to know was that people mysteriously disappear at that subway station, there's an abandoned tunnel and the girl suddenly disappears.
They could've easily wrapped all of this up in the first 30 minute and spend the rest of the movie creeping round the abandoned tunnels and escaping from the cannibal. It would've been really cool to see this kind of movie done in that unique 70's way.