The Doctor and Romana track the third segment of the Key to Time to the vicinity of an ancient stone circle on Earth. But sinister forces are at work and the stones hide a secret.

The leaders of a druidic cult have been killed and it seems that the stones from the stone circle are alive and have a taste for human blood.

As the blood hungry Ogri close in, the Doctor launches a desperate attempt to rescue Romana from hyperspace.

The Doctor releases two alien justice machines from imprisonment who sentenc him to death. Meanwhile Romana urgently searches for clues that will reveal Vivien Fay’s true identity.