Supergirl helps Winn face his greatest fear. After Alex sets out to find evidence against Lex, Brainy must decide between helping his friend or continuing to secretly work for Lex.

Mxyzptlk returns with a proposition for Kara – what if she could go back in time and tell Lena her secret before Lex did, would things turn out different? Looking back over key moments throughout the series, Kara must decide if she wants to change history to become friends with Lena again.

Supergirl intervenes when a building in the Heights that was set aside for low income housing is suddenly at risk to be sold to a major corporation. Supergirl recruits Orlando to help her win over the city, but things go awry when Nyxly shows up. Meanwhile, Nia trains with her mother.

Supergirl and team must stop Nyxly from vanquishing a familiar face from Supergirl's past - Mr. Mxyzptlk. Mxy returns and explains Nyxly's dark history to the super team in the best way he knows how - in song form. Meanwhile, Lena visits her mother's birthplace in Newfoundland, eager to dig into her past but is shocked by the small town's icy reception towards her.