WARNING: The following article contains spoilers for the Supergirl Season 4 finale "The Quest for Peace."
Supergirl's Season 4 finale ended on major cliffhangers for several characters, while also teeing up for "Crisis on Infinite Earths," the fall's hotly anticipated Arrowverse crossover.
One of the biggest question involves Lena Luthor. After she mortally wounds her brother Lex, shows her video of her best friend Kara Danvers turning into Supergirl, and informs her that everyone else was aware of her secret. As he takes his dying breath, he crows, "I'm about to die, but at least I lived without ever being a fool. You're left you with no one and nothing."
The revelation clearly rattles Lena, yet afterward she arrives at game night with Kara and the rest of the gang, and acts as if nothing has changed. Although Kara indicates to Alex that she wants to tell Lena the truth, her sister insists that Lena has been through enough; her identity can remain secret for a while longer.
However, perhaps Kara should have gone with her instincts, because when Lena is alone in her office, she breaks the glass of a frame containing a photo of her, Kara and Alex. That doesn't bode well. But is Lena merely upset because she believes her friends betrayed her, or will her anger blossom into something more sinister?
With everything that occurs in the episode, everyone kind of forgets about Eve Teschmacher. She attempts to leave National City when she's approached by an old woman, whose words suggest Eve should know her, or at least who she represents. It also becomes clear that Eve's actions to help Lex were at the behest of that organization.
"Lex was supposed to move the needle," the woman says. "He failed." Eve asks to be released from her obligation to the organization, but the woman denies her request. Then she ominously claims, "Leviathan is everywhere. Leviathan is everyone. And Leviathan is coming." In DC comics, Leviathan is a shadowy criminal organization that creates surgically or genetically altered superhumans.
The final moments of the season are dedicated to a surprise revelation that may have some bearing on "Crisis on Infinite Earths," and definitely will impact J'onn J'onzz. A hooded figure steps through a portal and is approached by The Monitor, the cosmic entity that was pulling the strings during the Arrowverse's "Elseworlds" crossover. The Monitor already showed up in the last few moments of Arrow's finale, and has a good idea of what the coming Crisis may bring.
That isn't mentioned in his exchange with the hooded figure, however. Instead, the Monitor tells him he brought him to Earth so he can avenge himself "against the brother who wronged" him. The figure pulls off his hood to reveal he's a Green Martian, and that he's coming for J'onn J'onzz. That means J'onn has a brother who's still alive, and apparently J'onn did something terrible to earn his wrath.
That obviously isn't good news for J'onn. This also indicates that the Monitor is still pulling strings to move pieces in place for some unknown end. Why he would want J'onn's brother to be working against the hero as the impending Crisis approaches, though, is unclear.
All these cliffhangers will likely begin to pay off off when Supergirl returns this fall for its fifth season.
Airing next season on Sundays at 9 p.m. ET/PT on The CW, Supergirl stars Melissa Benoist as Kara Danvers, David Harewood as Martian Manhunter, Mehcad Brooks as Jimmy Olsen and Chyler Leigh as Alex Danvers.