Suddenly, the Worm-mobile popped out into a railway tunnel. "Ah!" said the Doctor. "This is the underground railway. If we follow it, we will soon be in the city centre. How usefull!"

He pushed a button and some wheels came out under the Worm-mobile so that it could run on the railway lines. The signals showed it was going the right way and would not meet a train.

Then the Worm-mobile reached an underground station. The people on the platform were amazed to see Miss Nettles getting out, but she took no notice of them.

Doctor Snuggles took the Worm-mobile to the bottom of the escalator and waited for her to come back. Quite a crowd came to chat to him and have a look at the unusual Worm-mobile