The British space explorers, searching inside a Venusian volcano for Captain Wilson, are hunted down by a primitive species of men. Making their escape, they are trapped by roof falls and molten lava as the volcano erupts.

The astronauts have trekked across the vast Venusian desert to return to their rocket. But as they near MR4, volcanic ash sets the jungle aflame - and MR4 is in the centre of the inferno.