Lotor rejoices at the idea he's finally found a way to open the power at Claw Mountain on Arus and access it for his own ends (though he doesn't yet know how to harness the power). Meanwhile, the Voltron Force return from a strategy meeting at Galaxy Garrison, and Lance and Keith bicker about commanding leadership style. Allura interrupts saying there are strange readings at the threshold at Claw Mountain. They arrive to find the gateway open and active, and putting out a whole lot of energy. They don't initially notice Lotor, who then traps Black Lion and ambushes the other lions.
Lance decides to go straight for Lotor. He ends up unable to break free of Lotor's ship, while Keith frees himself. Lotor's ship enters Claw Mountain with Lance still attached. Pidge tells Keith to lock on to the mission decoder signal to plot a vector to locate Lance.
On the other side, the lions are their Stealth Voltron variants. They come face to face with another Voltron -- with a slightly different color scheme -- commanded by a courteous, narcissistic (yet aggressive), pre-Cyborg Lotor. The lions finally take ultra-stealth mode and escape. They're contacted by Lance who chastizes them for non standard uniforms and to get back to Castle Doom immediately.
Meanwhile, at the Castle of Lions, the cyborg Lotor pleads with his alternate self to help him conquer other universes, but the alternate Lotor isn't buying. He's content enough, where cyborg-Lotor is not. Cyborg Lotor also learns that Allura's considered a problem child whereas the alternate Lotor has a girlfriend in the beautiful youthful version of Haggar who is simply a semi-capable parlor trick performer.
Cyborg Lotor presents the alternate Lotor a data disk with a plan that finally rouses his excitement simply because it is entertaining. But not before Haggar botches yet another parlor trick, for which alternate Lotor praises her.
At Castle Doom, the two Voltron Forces sort things out. Keith tries to lecture his rebellious self around, while Allura lectures her floozy alternate who prefers boarding with Keith (a parallel to the affection the main Keith and Allura never have shown each other in this series). Alternate Hunk is revealed to be the group's intellect, while Alternate Pidge plays the jester doing whatever he's told.
Calm headed Alternate Lance realizes there is no other version of him with them. Keith explains their Lance got sucked through the rift with Lotor, which Alternate Lance says would explain their Lotor building ships at an accelerated rate at the Castle of Lions (which Allura is mortified that the alternate Lotor controls). Alternate Lotor has not been challenged here because this Lance believes in being cautious. Pidge and the Alternate Hunk locate Lance's homing beacon.
They find Lance with Alternate Coran living in the woods after Lotor and Haggar tricked him out of his lions. While some of the team fix Red Lion, Alternate Coran gives Allura Alfor's ring to call on the lion spirits if they can retake the castle (and later, taking Alternate Coran on her speeder, Allura is relieved someone shows a level head in both worlds). The alternates are dropped off to take the castle back while the lions plan to take on Lotor in Voltron and his fleet though Lance laments Red Lion's not fully recharged; Keith tells him to join them when he can.
The attack begins against Lotor, who traps the lions in an energy beam from the Blazing Sword. Lance joins the party and rescues them just in time. Together they form Stealth Voltron. Meanwhile, the other team takes the castle and Coran calls forth the Lion Spirits to re-energize and give hope to the rebel alternate Voltron Force. They are absorbed into the outcast spirits of the metal lions and placed into the cockpits of Voltron, casting cyborg Lotor out and into the Doom ship where Alternate Haggar and Lotor were resting. Together the two Voltrons team up and destroy the fleet.
The Alternate Voltron Force thanks the regular Voltron Force for helping them find their destiny. Meanwhile, the alternate Lotor tries to be mad and can't.
Lance is the last to eject from the parallel dimension and the others tell him that they never went in after him and in fact insists he needs a brain scan. He tells them about the people he met, and they laugh it off as something he dreamed out. Viewers are left to wonder if it was all in Lance's head or an unexplained phenomena....