Kellman arrives and the Cyberleader announces that Doctor, Lester, and Stevenson are alive but neutralized, and are needed for their plan. Kellman searches the Doctor for identification, without much luck.
Harry and Sarah Jane are brought before Tyrum and try to explain what they're doing. Kellman shows the Cyberleader a map of the transmit receptors he placed on Voga. The Doctor taunts the Cybermen into revealing their plan of using three "animal specimens" to destroy Voga. The Cyberleader confronts Kellman over the fact that Harry and Sarah Jane were transmatted down and how much they know.
One of Tyrum's militia offers Vorus' Guardians a cease-fire. On Nerva, Kellman insists on going down to Voga to check out the transmit receptors while the Cybermen bring in Cyberbomb harnesses.
Tyrum is certain Harry and Sarah Jane know something that Vorus believes is important, and wants them dead to protect his secrets. Tyrum wonders if Vorus has brought the Cybermen down upon them and asks them to go with him to confront Vorus.
The Doctor taunts the Cyberleader further and notes the humans designed the glitter gun and destroyed the Cybermen. The Cyberleader reveals he has enough parts to build a new Cyberarmy once they've destroyed Voga. The Cyberleader throws the Doctor into one of the Cyberbombs and demands answers about Kellman, but the Cyberleader secretly signals one of his men who grabs the Doctor and prevents the bomb's detonation.
On Voga, Kellman looks for Vorus and runs into Tyrum's men, who take him prisoner. The Cyberleader reveals three bombs are sufficient to destroy Voga and the bombs will detonate if anyone tampers with them until they get to Voga's center. The Cyberleader notes they have 14 minutes to get clear and return by transmit beam. He also notes that if they deviate, he'll activate the bombs prematurely. The three men transmit down with two Cybermen to cover their departure through the shafts. Tyrum's militia open fire and the Doctor, Lester, and Stevenson head off while the Cybermen devastate the militia.
The three men figure that they can't trust the Cybermen but they have no choice but to continue on. The Cyberleader is monitoring their progress and is unconcerned about Kellman's fate. Tyrum interrogates Kellman who reveals he was working with Vorus and Nerva is a trap – Vorus will destroy the Beacon with a missile. Tyrum orders his militia to try and stop the Cybermen while he goes to meet Vorus.
Vorus' men open fire while Vorus checks on his missile. Hearing gunfire, he emerges and Tyrum says they should work together. Vorus shows them the missile while Sarah Jane heads back to the transmat. Kellman is concerned if she's captured she'll reveal the true plan to the Cybermen. Sarah Jane dodges enemy fire and transmits back up to Nerva.
The Cyberradar is being scrambled by the gold and the Cybermen can't differentiate between the signals The Cyberleader notes that the bombs will detonate as soon as they get to the core. Vorus boasts he had planned to bring his people out into the light but Tyrum points out he worked with a traitor and has endangered them all. Harry suggests they get to the core through the central shaft and they go to the plans.
The three bomb-carriers start crawling through the tunnels while Kellman and Harry find a branch off the central shaft but it's blocked. The Doctor on the other side of the blockage inadvertently knocks it loose and falls back, stunned by a rock. Kellman is killed in the cave-in as well. Harry goes through to the other side, spots the Doctor, and unwittingly prepares to remove the bomb...