The TARDIS arrives on the planet Telos where an Earth archaeological expedition, led by Professor Parry, is attempting to uncover the lost tombs of the Cybermen. With a lot of help from the Doctor the archaeologists en...展开ter the tombs. There, one of the party, Klieg, reveals himself and his business partner, Kaftan, to be planning to revive the Cybermen.
He wants to use their strength, allied with the intelligence of his own Brotherhood of Logicians, to create an invincible force for conquest. It transpires however that the tomb is actually a giant trap designed to lure humans suitable for conversion into further Cybermen - a fate that almost befalls Kaftan's assistant Toberman.
After fending off an attack by Cybermats - small but dangerous cybernetic creatures - the Doctor eventually defeats the revived Cybermen, led by their Controller, and reseals the tombs. The Controller is apparently destroyed in the process.