When the US military orders an investigation into the DEO with experimental technology that can read minds, the only way to keep Supergirl's identity safe is for J'onn to block everyone's memory of who she really is. For the first time in her life, Kara's secret identity really is a secret. To everyone.
What are the investigators really searching for? What's their end goal? Where did they get the technology? And most importantly, why is Alex acting so weird around Supergirl all of a sudden?