The Doctor’s plan has failed — and the truth is finally exposed.

In Part Four of The Crucible of Terror, the deception surrounding the Crucible is uncovered. What was believed to be Earth’s salvation is revealed as a doomsday weapon, feeding on the planet’s core and counting down to total annihilation. Betrayed by Eddic and outmanoeuvred by Drax, the Doctor realises he has been manipulated into placing the Earth itself in mortal danger.

With the TARDIS unable to breach the Crucible’s multidimensional shielding, humanity’s last hope rests on a desperate and dangerous alternative: UNIT’s experimental gravity weapon. As the planet trembles and earthquakes ripple across the globe, Drax closes in.

The fate of the world hangs by a thread as the Crucible begins to rise…