DC Animated Universe

"Dark Heart" is the tenth episode of the first season of Justice League Unlimited, and the tenth of the overall series. It originally aired on December 11, 2004.


In the Nevada desert, a large alien construct lands on a mesa in an area which includes three neighboring towns. Huge spider-like robots emerge from the construct and proceed to spread over the area!

With General Wade Eiling in command, the United States Army arrives to try to keep the alien robots from overrunning the region. The army does what it can, but their weapons are ineffective against the alien threat. The full force of the Justice League is called in and Batman determines that the construct and the robots absorb local matter in order to grow bigger. Flying in his Batwing, he dumps an ice-bomb on to the structure in order to freeze it. The rest of the League then engage the spider-like robots but before long the machines are numbering in their thousands and are increasing.

The Watchtower's Binary Fusion Generator cannon gigs a trench around the Dark Heart

The Watchtower's Binary Fusion Generator cannon digs a trench around the Dark Heart.

To buy time, J'onn J'onzz tells the League and Army forces to pull back, clearing the area for the Watchtower's Binary Fusion Generator, an energy cannon "with the punch of a small nuclear weapon". From orbit, the cannon fires, digging a trench around the mesa to halt the aliens' advance, buying time to evacuate the nearby towns. Using his x-ray vision, Superman then discovers that at the centre of the alien structure is a Dark Heart which is replicated in each of the attack robots.

Since this alien invasion appears to be based on nanotechnology, Batman suggests that they consult the Atom, aka Professor Ray Palmer, an expert in the field. The energy cannon used up so much of the Watchtower's power that they cannot use its teleportation system so Superman flies to Boston where Palmer works in the physics department of a local university.

League fights Dark Hart

The League fights the Dark Heart's robots.

Superman takes the Atom back to Nevada. By the time they get there, the alien robots have overcome the trench and now number in hundreds of thousands. New robots, in the form of attack dogs, have now joined in the fight, making it even more difficult for the Leaguers to contain the threat. Observing the battle, the Atom explains that the robots can use any kind of matter in order to replicate and repair themselves when damaged and that they will continue until the whole of Earth is consumed! The only solution is for him to get inside the original structure and destroy the core program.

With the support of other flyers, such as Steel, Doctor Light, Green Lantern John Stewart and the Ray, Wonder Woman gets the Atom to the structure where he shrinks down to micro size and goes inside it. At the centre of the construct, Atom accesses its memory and learns that it was a war machine built by aliens as part of a galactic war. It destroyed its creators' enemies but then proceeded to other planets and destroyed them as well as part of its program, unaware that they were not involved in the original war.

Atom stops heart flow

The Atom disrupts the Dark Heart's blood flow.

Atom himself is attacked by the construct's internal defenses but evades them and eventually finds the Dark Heart's core control. Outside, the Leaguers are being overwhelmed by the robots which have become even bigger and more aggressive to the point that even the most powerful members are finding it hard to fight back. Atom's attempts to destroy the Dark Heart with his fists are in vain. He then notices some tubes that feed the Heart with liquefied matter. By blocking one of the tubes, he causes the liquefied matter to build up, break out of the tube, causing a flash flood which fills the construct and destroys it. Outside, receiving no further instructions from the main Dark Heart, the attack robots shut down and deactivate, moments before they were about to overrun the Justice League.

Eiling confronts league

General Eiling does not hide his hostility for the League.

With the invasion over, the Army gathers up the remains of the Dark Heart. Superman expresses concern for the material falling into the wrong hands, but General Eiling makes it clear that he intends to use it to find a way to counter the Justice League, citing the powerful weapon that they have in the Watchtower pointing down on Earth. Atom fears that if the Dark Heart is reactivated it will also destroy everything on Earth, just as it destroyed everything else it encountered before. Superman assures him that they won't let it.


Background information[]

Home video releases[]

Production inconsistencies[]

  • In an early scene where Green Arrow and Crimson Avenger are fighting the mechanical spiders, Aquaman can be seen coming down a Javelin ramp. He does not appear in any subsequent scenes and is unlikely to have been involved in a crisis which takes place in the middle of the Nevada desert and does not directly threaten the sea or Atlantis.


  • Bruce Timm has stated that Warren Ellis was hired to write this episode due to the fact that the original vision for the show was to be an anthology series.[1]
  • In this episode, Atom's DCAU base of operations is established as Boston. In the comics, Atom is a superhero/college professor who lives in the fictional city Ivy Town.
  • Atom is seen in a petri dish fighting a cell-sized monster (car sized to him). In Frank Miller's comic The Dark Knight Strikes Again Atom is found in a similar predicament.
  • This marks the final time in the series where the opening title sequence uses clips from the episode it is featured in.
  • Atom mentions the theories of John von Neumann.
  • Final appearance of the Batwing in the DCAU.


Actor Role
George Newbern Superman
Soldier (uncredited)
Pilot (uncredited)
Carl Lumbly J'onn J'onzz
Pilot (uncredited)
Kevin Conroy Batman
Atom-Smasher (uncredited)
Susan Eisenberg Wonder Woman
John C. McGinley The Atom
J.K. Simmons General Wade Eiling
Michael Beach Commander
Billy (uncredited)
Catherine Cavadini Katie
Billy's girlfriend (uncredited)

Uncredited appearances[]


(In a petri dish, a tiny Atom is ambushed by a faulty nanobot.)
Atom: He's bigger than my car now, Katie. Personally, I blame you.
Katie: How can it possibly be my fault?
Atom: Because otherwise it would be my fault. That can't be right: I'm a professor.

Batman: (falling from the sky) Batman to all points. I could use some air support... since I can't fly... at all. (reaching the ground) Now would be good.

Wonder Woman: (fighting robots while holding the tiny Atom in her fist) I need both hands, Professor Palmer!
(She slips the Atom into her cleavage.)

Atom: This is incredible. Every atom of it is filled with a book's worth of information. It's beautifully simple, it—
Batman: Save it for the autopsy.

Superman: (referring to the remains of the Dark Heart) I don't suppose you need any help destroying that? Wouldn't want that technology falling into the wrong hands.
General Wade Eiling: We can learn a lot from it. It almost beat the Justice League after all.
Wonder Woman: Why would you need something to do that, General?
General Wade Eiling: Oh, I don't know. Maybe because it turns out that the Justice League has had a secret space-based weapon of mass-destruction all along. And we're going to be talking about that some day, believe me. Ma'am.

Atom: Amazing. Show him a weapon that destroyed its creators and every other thing it saw, and he wants to play with it. What's to stop history from repeating itself right here on Earth?
Superman: We are.


  1. Top 10 Toons on the Air - 1.) Justice League Unlimited by Mike Cotton - Wizard Magazine #168 October 2005