Inhumanoids (1986)

S1E4 The Evil That Lies Within (4)

Blackthorne, under duress, reveals a secret to the Inhumanoids, who then storm a Soviet air base and seize several nuclear warheads. Claiming a change of heart, he warns Earth Corps the missiles are aimed at splitting the Earth's crust from its mantle. Venturing deep underground to stop the attack, the team realizes they've walked into a trap—the real target is the planet's core. Desperate, they persuade D'Compose, who fears Metlar's madness will doom them all, to open the gates of Infernac. Racing against time, they disarm enough warheads to prevent total annihilation.