So yes, James Olsen wants to tell Kara he's the mysterious Guardian and he's jealous that Mon-El gets to train with Supergirl and has her blessing to fight crime. And yes, the return of Supergirl's nemesis LiveWire (Kara isn't too happy about having a nemesis by the way) has her in jail raving to her psychiatrist about how she's going to kill the Girl of Steel. And yes, M'Gann, the White Martian refugee who saved J'onn with her blood and now languishes in a DEO prison starts to go mad (''Blood! Death! Beautiful War!") and collapses into a psychic coma. And every one of those is an important thing that someone within the cast has to deal with.
LiveWire escapes, with help, and attacks the NCPD, sending Kara and Mon-El out on their first mission together. J'onn, dealing with his White Martian issues refuses to mind meld with M'Gann in an attempt to save her. James, in Guardian gear goes to help with LiveWire, who's NOT the original villain, but another LiveWire and the "guard" who helped her escape, both of whom have similar powers. It starts to get really interesting here when Mon-El, defying Kara's orders to get the cops out, tries to save Kara from a double electric beat down. His mishap leads to a stray lightning bolt that Guardian saves a cop from but is struck down by. Unconscious and unmasked, James (along with Wynn and Alex) comes to, having to face the wrath of an angry Supergirl, who does her best Batman impersonation. James, in her mind, with no powers isn't made for crime fighting while he believes that it's the one thing that makes him feel alive. Her Batman impersonation continues when she calls out Mon-El for his mistake during the fight and benches him for not fighting the good fight for the right reasons. Cue to the original LiveWire, strapped down and having her power siphoned by an unknown doctor.
The whole jail break was staged but Wynn and James track her down unbeknownst to Kara. A remorseful J'onn changes his mind and needs her and Alex to help him save M'gann from whatever has overcome her mind. In the meld she reveals that she turned on the other White Martians when they told her to kill a Green Martian child. J'onn's forgiveness frees her but there is more to her sickness. The unnamed doctor's plan was to copy LiveWire's powers and sell them to the highest bidder. Guardian, who had Wynn track LiveWire, and Mon-El, who followed him are both subdued by the very same doctor who'd powered himself first. Only Supergirl's timely arrival saved the boys and LiveWire from their pending demise and the three heroes made short work of the two electric powered mercenaries, while LiveWire herself leaves after being persuaded by Supergirl to save his life.