Ming the Merciless tells Octon of his frustrations by the slow progress of his station build on earth and wants his robot forces to accelerate. Suddenly a warning alert flashes and the two observe an unknown fleet of ships bearing down on Earth. Ming order Octon to break into their code to figure out who the mysterious fleet might be.

Meanwhile, at Mandrake’s mansion, the young Defenders wait as Rick Gordon prepares to activate Dynak X, the most advanced computer ever built. Mandrake reveals that Dynak X is unique because it contains the "human essence" of Rick's mother (an unnamed Dale Arden), preserved in a crystal. We get a quick flashback of Zuffy (the space alien) retrieving the crystal. Flash gives Rick the go ahead to activate the computer. Kshin muses that perhaps the team could use the newly christened computer to help find a permanent headquarters, as Mandrake's mansion (Xanadu) is insufficient for global defense. LJ counters that Xanadu is fine, but Flash jumps in with a quick retort. A homesick Jedda tells her father the Phantom that she misses their home, the skull cave. Suddenly, a warning alarm flashes and Dynak X alerts the team to an cadre of incoming ships that are, as of yet, unidentified.

Back at Ming’s headquarters, Octon relays that code from the transmission is linked to Flash Gordon; Ming instantly orders the transmission be traced. 

Flash recognizes the ship fleet and welcomes Morkon of the Cryl, a friendly alien race who have arrived to help build the new base. Morkon refers to Flash as “old friend" and asks if the team has created a name for their new base? Flash answers "Monitor," from which they will monitor Ming's activities. Unknown to the team, Ming is listening in to their transmission with the Cryl and overhears Flash reiterate the name of the team as Defenders of the Earth.

At Ming’s insistence, Octon orders Garax to follow the Cryl to the Defenders location and then launches an attack, nearly destroying the Dynak X unit before the heroes can retaliate in their own starships. Immediately, Mings forces begin firing on the Cryl and Flash realizes their transmission has been compromised. He orders Rick to include “more shielding” to protect the computer. When Morkon implores Flash to assist against the attack, Flash jumps into his attack ship and races to battle. At one point Garax recognizes that Xanadu is location the Cryl are traveling to and prepares to attack the mansion directly. However, Mandrake intervenes with an illusion that the mansion is floated towards Garax’s ship; Garax manages a retreat, but one of the robot ships is destroyed by the illusion. At one point an overexcited Kshin encourages Flash to beat out Mings' forces, but is instantly admonished by Mandrake and sent away. Kshin quickly leaves the area and Mandrake calls out to him, but to Kshin still exits. Lothar dismisses the incident telling his friend that Ming might be easier to deal with than teenagers. 

Meanwhile, Flash continues to battle the robot army in the sky. Kshin and Zuffy (the space alien) manage their way to a cliff outside of Xanadu to watch the skirmish. At one point Kshin sees Flash might be in trouble and calls for him to look out. Kshin picks up a rock, hurling it at one of the attack ships which then blows up. Even Kshin seems surprised at that, but gets a knowing glance of thanks from Flash (they're all in this together, after all). Kshin attempts to make a quick exit but the robo-ship destroys the cliff path in front of him. Back at Xanadu, Rick warns his father of an ongoing onslaught of fighters. Being a master pilot and warrior, Flash is patient and leads the robot fighters into a path that is obscured by the light of the sun, at which point Flash and the Cryl swoop in and destroy the invaders. Kshin and Zuffy (the space alien) continue to watch the battle from the cliff and Ming, observing him through the transmission, orders Garax to take him alive so that Ming can use him as a lure for the defenders. 

Robot sentries drop from their ship to go after Kshin and Zuffy (the space alien). The writers favorite space alien seemingly finds a cave the two can escape to, however the pursuing sentries blast a hole big enough for themselves and continue to follow. In their escape Kshin realizes the cavern is immense and the duo continue to evade the robots. However, at one point, they appear cornered at another cliff and with the robots are upon them the cliff gives way and Kshin and Zuffy (the space alien) fall off from the cliff and land on an embankment just outside a pit of lava. The robot sentry’s attempt to pursue, however they get caught in the molten lava and begin to fire their ray guns erratically. Before being succumbed by the lava, one of the blaster bolts hits the cave wall and reveals yet another cavern to which Kshin and Zuffy (the space alien) attempt to make another escape. As it turns out, the two end up in the wine cellar of Xanadau where Jedda and Kisa find them; they’re safe for now.

With the team and the Cryl back together at Xanadu, Dynak X analyzes the cavern and determines it is large enough for a city. Flash says that it would be perfect for a base and Mandrake gives Kshin credit for the discovery saying he’ll make a good defender, but adds that he needs to follow orders. Dynak X interjects to warn that the mountain is a semi-active volcano. Jedda jumps in to say that the volcano can be capped and the power could be harnessed to give them unlimited energy (which they’re going to need if they plan to fight Ming). 

After an indeterminate period of time, with the help of the Cryl, a series of structures is now present in the cavern one of which will serve as the “cap” of the volcano. At one point the Phantom becomes concerned about Jedda and when he questions her, she again reiterates that she doesn’t think she’ll be happy because they are away from their home.  The Phantom tells her that she cannot return to their African village by herself and that he’s worried for her future. 

Back in his lair, Ming is infuriated by his initial failure. Octon tells Ming that there has been mass of energy detected at their initial area of attack and Ming surmises that this MUST be the Defenders headquarters. Garax requests that he be allowed to attack again, only this time from inside the base. Next, we see the Ice Robots attack, trapping the Defenders' ships inside the mountain.

Having caused a cave-in, the robot sentries continue their attack damaging the interior structures of the mountain base. Flash grabs one the Cryl’s laser cutters and uses it against the sentries. As the Phantom, Lothar, Mandrake and Jedda watch in disbelief, the Phantom steps up with an idea to use the sentries advantages again them. Calling on the power of 10 tigers (based on Jungle law) the Phantom swoops into action drawing their attention and fire. With the robots following the Phantom, Flash douses them with concrete which finishes the attack (for now). 

Back at Mings fortress, Ming quickly forgives Garax and reiterates to Octon his desire to have the base destroyed permanently. 

At Monitor Dynak X tells the team the damage isn’t permanent but once again, Ming’s forces show up to do damage. However because their still trapped inside, Lothar has Dynak X broadcast a fake SOS to the top of the volcano. Garax falls for the ruse and blasts the top of the volcano which creates an opening the Defenders needed. The team raise the crown through the newly created mountain top, while Rick fills the base of the crown with water (thus presenting a camouflage). The team (with the continued aid of the Cryl) launch their attack fighters to go after the robo-sentries. During this battle, one of the sentry ships crashes into the mountain causing a break which has a cascade effect on the base power supply and they begin to lose energy and blow the volcano. Utilizing her telepathic link, Jedda sends Kisa into a narrow shaft to plant a relief explosive. 

The resulting explosion appears to Ming as a volcanic eruption and he assumes the base (along with the Defenders in it) have been destroyed. 

Again, Jedda relays to the Phantom that she does not want to stay at Monitor; the Phantom, once again, reminds her of the promise he made (for the two of them). Rick submerges the crown back into the volcano, now masked by the water present at the apex. The Defenders eject construction debris with the intent to convince Ming that the base was, in fact, destroyed. Fooled, Ming retreats, believing his enemies are dead, even though Octon tells him there is still quite a bit of residual energy coming from the mountain. Ming, however, continues to gloat in the idea of his victory. 

As the team inspect the damage done, Morkon brings everyone down into a newly created part of the mountain’s cavern. Heat and steam present create an atmosphere that remains at a constant 88 degree temperature. This Jedda points out is a similar climate to their village and the Phantom uses this opportunity to posit the creation of a second Skull Cave. 

Back at Mings base, he notes that the Cryl are leaving the area and once agin, Octon has to point out that not only is Flash Gordon alive, but that he is also escorting the Cryl. Ming swears that Flash will not be alive for much longer. 

The End. 

• This episode is the first to feature the alternate introduction in which the title at the very end of the intro sequence zooms into the distance in a different way

• As in the first episode, Flash Gordon's wife (Dale Arden) is never named; even when her "essence" is used in the creation of Dynak X *

• Mandrake performs one his most impressive feats in this episode, convincing Ming's invading forces that his entire mansion is floating in the skies above the mountain where Monitor is based

• The Cryl was the name of the empire that destroyed themselves in Forbidden Planet, the 1956 science-fiction movie (starring Leslie Neilson and Walter Pidgeon)**

*In Star Comics Defenders of the Earth, Dale's name is featured prominently in the first two issues

**Note, in the Star Comics (issue 02), the leader is named as Morbius (not Morkon)