Supergirl and the DEO are called on to protect the President when she comes to National City to sign her Alien Amnesty Act. However, a hostile alien threatens to kill the President and anyone who gets in its way. Meanwhile, Alex meets Maggie Sawyer, a detective with the NCPD's science division, and Snapper challenges James' authority.

Cadmus provides a gang of crooks with alien weaponry in an attempt to spread fear and panic among the populace. Meanwhile, Kara tries to mentor Mon-El with minimal success, and James decides that he wants to be a superhero.