M'gann's White Martian mate Armek comes to Earth to bring her back to face justice for her "treachery' When she takes refuge in the DEO, Armek infiltrates the building and uses his shapeshifting powers to spread confusion.

It's Valentine's Day, and Kara finds herself dealing with the amorous advances of Mxyzptlk, a fifth-dimensional being with unlimited magical powers. Meanwhile, Alex discovers that Maggie hates Valentine's Day, while an alien woman hits on Winn.