On Arus, the team is unaware of the gathering threat, and in repeat footage from Magnetic Attraction, they're out in the countryside practicing their hand-to-hand fighting skills. After their training session, they discuss their training backgrounds with the boys thinking they have it over the Princess being that they were trained by the Academy. Princess explains how Arus has had battle training going back ages, which brings them to the topic of the great fighters of yore. There were Lion fighters, which is where Alfor got the idea for the robot lions, but there were also Tiger fighters. Gee, all we need are some bear fighters and we can all say "oh my!"
Back on Doom, Stride the Tiger Fighter arrives and Cossack - not knowing its signifigance, wants to shoot it down. Zarkon knows better but allows him to try anyway. Of course, his firepower is no match for the tiger ship.
Zarkon tells Stride that Arus has challenged him to a fight for honor, and he is willing to fight for that. Though he seems aware of Zarkon's evil ways and despite the fact that Alfor and Stride's father fought on the same side, Stride believes Zarkon and is off to Arus. Lotor is skeptical Zarkon's plan will work, but has to prepare for Merla's arrival. Plus, since honor is involved, the Lions will have to fight him one on one and Zarkon is sure they can't beat the tiger fighter that way.
As Merla arrives, Lotor doesn't like all the attention she garners. Lotor is confident she'll be smitten with him however, and bow to him. Boy is he in for a shock - Merla is her own woman and pretty much has him pegged as "brutish and dim-witted" from the start. Ouch.
Once inside Castle Doom, Merla shows the respect to Zarkon she denied Lotor and he is bitter. Her terms for joining with Zarkon is that their kingdoms merge equally. When Lotor protests, he also accuses her of not paying proper respect earlier which she denies. Then, she shows off her telepathic skills by communicating with Lotor with her mind. She has a power of persuasion and convinces him to admit he made a mistake in his accusations.
When that works, Merla works her powers on Zarkon to convince him that it's a good idea for her and her crew to go help Stride take Arus - her motivation is she doesn't want Zarkon having all the glory for himself. Merla is a woman who knows how to get her way.
Meanwhile, Stride arrives on Arus to meet the "challenge". Princess recognizes Stride and explains to Keith who he is and the code by which he lives. They have to fight him. The fight rages on in space between Keith and Stride while the other pilots are helpless and just watch - honor dictates they can't intervene.
But Merla arrives and shoots both pilots down. Both pilots get out of their downed ships and continue to fight with swords. Keith is bested, but Stride spares him.
As they're making nice, Merla shows up with some soldiers to take them captive. But the other Lions bail them out. In response, Merla has a robeast launched and although Stride wants to take on the beast alone, Voltron also joins in the fray. His blazing sword saves the day.
Merla vows revenge on Voltron for suffering her first ever defeat, and Stride is patched up by the Princess.