It's all-out battle with the brand-new and deadlier-than-ever Fatal Five! But the story takes a strange turn when one of the villains sacrifices her life for the Legion!

As Emerald Empress revealed that Sensor Girl was actually Princess Projectra, the other Legions battling the Fatal Five take that opportunity to escape and regroup. Meanwhile, Brainiac 5 has come to the same conclusion about Sensor Girl's secret identity after some careful speculation and informed his fellow teammates. The Fatal Five search for the runaway Legionnaires and eventually find them, entering into another battle. Mentalla decides to take this moment to betray the Fatal Five, mentally manipulating Emerald Empress and Flare to summon more Legionnaires. She reveals that she never intended to work for the Fatal Five; she simply wanted to show the Legion that she was worthy of joining their ranks. Emerald Empress does not take the betrayal lightly and kills Mentalla immediately. Soon, only Sensor Girl is standing to face the Fatal Five and she is able to use her enhanced abilities to fight them long enough for Legion reinforcements to arrive.