Picking up from last issue, Supergirl has just been hit by an energy blast from Cat Grant, she recovers to find the whole thing was an illusion (though she was hit by something). Before she can investigate further she loses control of her powers. Meanwhile the Emerald Empress and Selena pluck a hair follicle from Solomon Grundy at Arkham and magically clone him, while Magog & Indigo ad "bio-Mechanical Enhancements", basically growing him larger, stronger, and easier to control (I.e. more like Validus). So the New Fatal Five is Emerald Empress, Selena, Indigo, Magog and an enhanced Grundy clone.
Empress says she's already confronted Saturn Girl and Imra revealed to her that it wasn't Saturn Girl who ultimately defeats her but Supergirl (No word on what she did with Imra afterwards). Empress has convinced the other members of the Five that Supergirl similarly ends their lineages in the future, so they are banding together to stop her in the "Now". While Supergirl tries to get her powers under control to confront a rampaging Grundy, Selena and the Empress ambush Cat and Chase respectively, looking to turn Supergirl's allies against her.