A crisis develops when a noxious liquid leaks out as drilling progresses - the green poison has a grotesquely debilitating effect on human beings.

As the Earth's plight worsens, the Doctor is trapped in a parallel world, unable to rescue the planet and its inhabitants from the destructive force of Inferno ...
 

"If you break through the Earth's crust now you'll release forces you never dreamed existed!"

20th century Earth. An unhinged scientist, Professor Stahlman, is attempting the first penetration of the Earth's crust in a top secret drilling project called Inferno. His purpose? To tap into a new energy source at the core. But at what cost?

When the Doctor is called to Earth with his companion Liz Shaw to oversee the project, he soon develops grave misgivings. Things begin to go verywrong when a mysterious green substance leaks from the drillhead. A substance which turns all who come in contact with it into alien primeval creatures called Primords.

Meanwhile the Doictor finds himself transported into a parallel universe identical to 20th Century Earth. The mystery deepens as he finds that although the place, time and people are all the same, no-one seems to know who he is.

Only one thing is certain: the drilling must be stopped before the full force of the energy from the core is unleashed, destroying not only this Earth but the one the Doctor has left behind...

Originally transmitted 9 May - 20 June 1970, this Seven part adventure starring Jon Pertwee was the last to feature the original TARDIS console which dated back to 1963.

Running time: 167 mins approx.

Produced by Barry Letts
Directed by Doglas Camfield
Cover Illustration by Colin Howard