A black kryptonite explosion splits Lex in two and his evil side – Alexander – is released. Alexander imprisons Lex in the mansion then gives full vent to his evil side. He threatens to evict Lana from the Talon unless she becomes his mate, jousts with Lionel, and tries to kill Clark and Chloe when they figure out his secret.
Preview
When a LuthorCorp kryptonite experiment goes up in smoke, a freak explosion splits Lex Luthor into two distinct entities: one who embodies his gentle, remorseful side, and another driven entirely by ruthless ambition, dark impulses, and pure, unfiltered megalomania. As the evil “Alexander” seizes control of the mansion and locks his better half in the cellar, he sets out to systematically dismantle anyone who ever dared to hold him back.
With Alexander setting his calculating eyes on Lana, manipulating Jonathan, and even dangling Chloe’s friendship over the edge, Clark Kent finds himself facing his best friend’s darkest potential far sooner than expected. Will Clark realize the truth in time to stop Alexander from making deadly moves on the Kent farm—or is this the moment the legendary Luthor feud truly begins?
Episode Review
If you ask any Smallville fan to name the top five essential episodes of the entire ten-season run, “Onyx” is almost guaranteed to make the list. Directed by Terrence O’Hara, this episode is nothing short of an absolute tour-de-force showcase for Michael Rosenbaum. We’ve spent nearly four seasons watching Lex battle his inner darkness, trying desperately to escape his father Lionel’s shadow and prove he’s a good man. “Onyx” essentially hits the fast-forward button on Lex’s destiny, letting Rosenbaum rip off the gloves and deliver the cold, calculating, operatic supervillain we always knew was lurking beneath the surface.
What makes the episode so compelling isn’t just the comic book trope of a “good vs. evil twin split”—it’s the chilling realization that Alexander isn’t an alien clone or an external demon; he is genuinely just the uninhibited dark side of Lex Luthor. From the subtle smirk when he handles a firearm to the terrifying delivery of his monologue about ruling the world while Clark merely “saves” people, Rosenbaum commands every frame. It serves as the ultimate foreshadowing for the future of the series and the wider Superman mythos. Add in Chloe secretly guarding Clark’s secret while watching evil Lex corner him, and you get an electrifying, high-stakes hour of television.
Cast & “Freak of the Week”
Main Cast
- Tom Welling as Clark Kent
- Kristin Kreuk as Lana Lang
- Michael Rosenbaum as Lex Luthor / Alexander
- Allison Mack as Chloe Sullivan
- John Glover as Lionel Luthor
- Annette O’Toole as Martha Kent
- John Schneider as Jonathan Kent
“Freak of the Week” / Special Guest Star
- Guest Star: Michael Rosenbaum playing double duty as Alexander (Evil Lex) and Lex (Good Lex).
- Freak Profile: While most weeks give us an angsty teen infected by green rocks with magnetic powers or stretchy limbs, this week’s “Freak” is home-grown Luthor royalty. Splitting via black kryptonite heating, Alexander has zero actual superpowers beyond supreme intellect, sociopathic charm, lethal martial arts skills, and endless wealth. He is, by far, the most dangerous threat Smallville has seen all season.
- Malcolm Stewart as Dr. Sinclair: The head LuthorCorp scientist who accidentally causes the split during his high-heat agrarian kryptonite experiments.
Special Effects & Visuals
For mid-2000s network television, the split-screen and compositing effects used to put Michael Rosenbaum in the same frame with himself are remarkably solid! The lighting cues make a world of difference: soft, warm lighting for “Good Lex” and stark, high-contrast, predatory shadows for “Alexander.” The physical cues like Alexander wearing the sleek, dark suits while good Lex is stuck in a sweater sell the illusion even more than the CGI.
On the rougher side, the initial laboratory explosion with the black kryptonite looks a bit like a microwave full of tin foil going off in slow motion, complete with some classic early-2000s green-and-black digital fire. Also, Clark catching a speeding bullet at point-blank range still sports that slightly rubbery CGI hand blur, but the sheer coolness of Clark finally using his speed right in front of an unsuspecting villain makes it easy to forgive.
Music & Track Listing
- “I Want It All” by Depeche Mode — Plays during the scene where Alexander asserts his newfound dominance and prepares to reshape LuthorCorp in his own image.
- Original Score by Mark Snow — Special shoutout to the haunting, orchestral brass motifs Snow weaves in whenever Alexander embraces his villainy; it gives the whole episode a grand, cinematic weight reminiscent of classic theatrical Superman scores.
Rating
(5 / 5 Stars)
An all-time classic. Peak Smallville storytelling with Michael Rosenbaum firing on all cylinders.
Lessons & Becoming Superman
The Lesson: The Fragility of Identity & Balance
“Onyx” delivers a profound message about human nature: our goodness isn’t the absence of dark thoughts, but the conscious choice to master and resist them. Lex without his conscience becomes a monster, but Lex without his ambition and strength becomes entirely helpless. Balance is necessary to survive, but morality requires daily vigilance.
Connecting to the Superman Mythos
This episode serves as the psychological blueprint for the entire Clark Kent vs. Lex Luthor dynamic.
- The Tragic Inevitability: Up until now, Clark always held out hope that Lex could be saved from Lionel’s corrupting influence. “Onyx” shows Clark the terrifying truth: the darkness was inside Lex all along, and one day, this version of Lex is coming back permanently.
- The “Greatness” Speech: Alexander’s spine-tingling line: “I am a villain of the piece, Clark. I was born to lead people, not coddle them” is pure classic comic book villainy. It firmly establishes the philosophical divide: Superman protects humanity because he values life; Lex seeks to dominate humanity because he believes only he has the intellect to lead them.
- Clark’s Secret: Alexander’s obsession with discovering Clark’s secret foreshadows decades of comic lore where Lex’s arrogance makes him blind to Clark’s true nature until it’s forced into the open.
Complete Synopsis & Plot Breakdown
The episode opens inside a high-tech LuthorCorp agricultural research facility. Dr. Sinclair is conducting experiments on kryptonite-irradiated crops using extreme heat, hoping to supercharge growth. Lex arrives to shut down the reckless testing, but during an argument, a laser array overheats, striking a sample of green kryptonite and heating it until it transforms into glowing Black Kryptonite. The container bursts, causing a massive explosion that blasts Lex across the room. When the smoke clears, Lex is physically split into two distinct human beings: the meek, compassionate “Lex” and the cold, ruthless “Alexander.”
Alexander wastes no time. He immediately knocks out his good counterpart, locks him inside the sprawling wine cellar beneath the Luthor mansion, and assumes full control of the Luthor empire. When Jonathan Kent visits the mansion to discuss a lease renewal for the Talon, Alexander acts openly hostile, ripping up the agreement and demanding immediate full payment, shocking Jonathan with his sudden cruelty.
Alexander then pays a visit to Lana at the Talon, turning on the charm in a predatory, possessive way that creeps her out. When Lana resists his aggressive advances, Alexander hints that he takes whatever he wants.
In the cellar, Good Lex manages to escape his confinement through a service tunnel and stumbles out into the woods, eventually making his way to the Kent Farm. Battered and terrified, he begs Clark and his parents for protection, revealing that his dark side has taken physical form and intends to destroy everyone. Jonathan and Martha are initially skeptical of the wild story, but Clark realizes the danger after finding the scorched black kryptonite residue at the destroyed lab.
Alexander visits his newly “reformed” father, Lionel Luthor. Sensing something deeply wrong with his son, Lionel tries to appeal to Lex’s conscience, but Alexander brutally beats him, mocking Lionel’s religious turn and making it clear that the student has surpassed the master. Alexander reveals his ultimate goal: to eliminate every weakness in his life, starting with Clark Kent and the Kents.
Alexander arms himself with a gold-plated handgun and heads straight for the Kent Farm. Arriving at the barn, he corners Good Lex, Chloe, and Clark. Alexander gloats about his vision of world domination, declaring that while Clark wants to save the world, Alexander was born to rule it. He raises his pistol and shoots Jonathon.
Before Alexander can react further, Clark uses a heated fragment of the Black Kryptonite, utilizing its radiation to physically rejoin Alexander and Good Lex back into a single body. Lex collapses into unconsciousness.
The following day, Lex wakes up in the mansion, restored to his normal, unified self. Clark visits him, but a lingering awkwardness hangs in the air. Lex claims he only has foggy memories of what his dark half did, but his quiet, contemplative gaze out the window leaves Clark wondering just how much of Alexander is still sitting right in front of him.
Photos
Review Notes
OK 2 lex’s really
Evil lex killed the doc
He’s becoming monsanto
Oohh bad lex really is a pedo
Man bad Lex is BAD!
Well, that was lucky how the heat vision randomly did that.
Talk Ville: ONYX (S4E17) Meet the Villain of the Story, Keeping the Mask & Tapping Into Evil
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