A pair of archaeologists in Africa are examining the remains of prehistoric men. Behind them, the mountain disappears, revealing a cloaked Gorilla City, as a gorilla on a hover bike speeds out of the city while being pursued by other gorillas. However, the gorilla escapes his pursuers, who are forced to retreat back into the city after seeing the archaeologists. Another normal day on DCAU Earth.
In Central City, the Flash is showing off to two uninterested ladies until he sees a runaway van shoving aside cars heedlessly. The Flash chases after the van, while one of its passengers attempts to shoot at him with a futuristic pistol. The chase ends at a bridge, where the van and its occupants are captured by Green Lantern, who has arrived to assist the Flash. They find the van was carrying stolen radioactive isotopes and the drivers are research scientists at the institute from which the isotopes were stolen. Strangely, when the scientists wake up they claim to have no memory of what they were doing.
Flash and Green Lantern arrive at the institute to question the scientists’ colleague, Dr. Sarah Corwin, who states that she has no explanation for their behavior. While she speaks to Lantern, Flash notices a familiar gorilla among the lab’s test monkeys. The heroes then hear an unusual report of a gorilla driving a getaway car to escape the police. Flash manage to chase down the car and is surprised when the gorilla speaks. Suddenly, Corwin, hiding on a rooftop, blasts Flash with some kind of energy ray.
Flash has a series of bizarre hallucinations, then wakes up inside a jail cell. The police show him a surveillance tape of him stealing the isotopes from the police impound. His interrogation is cut short by the arrival of Lantern, who has paid Flash's bail to take him away, then angrily subjects Flash to another interrogation. Flash insists that he’s innocent, but can’t explain why he was stealing the isotopes. The last thing he can remember is stopping the talking gorilla.
Lantern is skeptical, but gives Flash the benefit of the doubt as they manage to track the gorilla down. The gorilla introduces himself as Solovar, chief of security for Gorilla City, a civilization of hyper-intelligent gorillas hidden from mankind. Their city has been peaceful until recently, when Grodd, a genius scientist, went rogue and developed a mind control helmet that he tried to use to take over the other gorillas. The authorities developed a resistance to the helmet and chased Grodd out, but now he's sworn revenge on the city. Solovar also says his investigation has found an email correspondence between Grodd and Corwin. Needing no further information, Flash streaks back to the institute, before Solovar can explain that he has a small supply of electronic headbands that will shield a person from Grodd’s mind control. By the time he and Lantern get to the institute, Grodd has already subdued Flash and placed him under mental control, and uses him to attack Lantern. Lantern knocks Flash out with difficulty, but Grodd and Corwin have escaped. Grodd has used the isotopes to power a machine in the heart of Central City, which he activates before he and Corwin speed away on his hover bike. Lantern and Solovar run to the machine, but then it gives off a colossal energy surge, like an explosion, that covers Central City and leaves nothing behind.
Green Lantern, Flash, and Solovar awake to find that Central City is covered in an invisible, impenetrable dome similar to Gorilla City's. The trio made their way into Central City and find Grodd holding court in the city square, with a crowd of people under his mind control. Lantern, Flash, and Solovar confront him, but Grodd sics his puppets on them, before fleeing with Corwin. The three escape the mob and track Grodd to a military base, where Grodd fires four nuclear missiles at Gorilla City. Green Lantern flies after the missiles, while Flash and Solovar deal with Grodd.
Meanwhile, the Justice League detect and investigate the disturbance in Central City. Soon they identify similar energy readings from Gorilla City, where they arrive, but are immediately captured by the city's security forces, who believe they are spies from the outside. Fortunately, the League break out of their imprisonment but are trapped by the shield. As they are being cornered by the security forces, the shield suddenly malfunctions and shuts down – Grodd left a sabotage device behind. At the same time, the gorillas detect the incoming missiles. To their surprise, the League offers to help them.
Green Lantern is able to neutralize two of the missiles, but debris from one of the missiles briefly knocks him out. As the remaining missiles are almost close to Gorilla City, the other Leaguers are awaiting. J'onn phases out the guidance system on one, causing it to crash harmlessly. Hawkgirl smashes the last missile with her mace, breaking it into pieces, but the warhead stage is still heading for the city. Wonder Woman flies into the missile's path and stops it from exploding, but she is crushed underneath it before it grinds to a stop. The normally stoic Batman furiously dig in the rubble under the missile, shouting Wonder Woman's name. When there is no response, he gives up, but then the missile body lifts, and Wonder Woman emerges, holding the guidance system. The city is safe. Wonder Woman realizes Batman's attempt to save her and kisses him on the cheek.
Grodd is angered that his plans are foiled and goes berserk and attacks Flash while Solovar is temporarily subdued. Flash is able to dodge his attacks at ease, but he then proposes a fair fight, and takes off his headband (despite Solovar's protests), inviting Grodd to take off his helmet. Grodd, of course, does no such thing. He activates his helmet but screams as it feeds back on itself, due to some subtle sabotage by Flash when he patted it down over Grodd's eyes. To his surprise, Corwin turns out to have not been under Grodd’s mind control – instead, she had genuinely fallen in love with him.
The League meets up in Gorilla City, where the leaders thank them for their help. Solovar shows them Grodd, now a brain-dead vegetable, bearing an almost comic resemblance to a zoo ape. However, as the League and Solovar walk away, the vacant look in Grodd’s eyes disappears, and they narrow with hatred...
Tropes:
- Adaptational Job Change: Solovar is depicted as the chief of security for Gorilla City here instead of its ruler as most incarnations are.
- Arbitrary Skepticism: Green Lantern is skeptical of Flash's claims that Solovar could talk and drive a car.Green Lantern: I'm expected to believe this?
Flash: Hey, we've both got a Martian's phone number on our speed dial! I think I deserve the benefit of the doubt here. - Are These Wires Important?: During the fight with Grodd in the climax, Flash pats his helmet down over his head while messing with him. Flash later reveals that when he did this he also subtly sabotaged the helmet by crossing a few wires, so when Grodd tries to use it later on Flash he ends up frying his own brain.
- Batman Gambit: By Flash of all people on Grodd. He anticipated Grodd would not honor a fair fight if he took off his protective headband, so he tricks him into doing it after Flash secretly rewired his mind-control device from his previous tussle with him.
- Canon Foreigner: Dr. Sarah Corwin was created for the show.
- Casanova Wannabe: The Flash is seen flirting with two unnamed women early in the episode, who clearly aren't interested in him. However, this seems to change after he saves them from getting hit by a car and one of them seems to regret not giving him her phone number.
- Cliffhanger Copout: The end of Part One has Grodd's machine give off an explosion-like energy surge that seemingly reduces Central City to a crater. The opening of Part Two reveals that Central City is actually under a dome similar to Gorilla City's and that the "crater" is actually an illusion meant to fool outsiders.
- Does Not Like Spam: Grodd hates bananas.
- The End... Or Is It?: After the League leaves, Grodd's blank expression turns into one of pure rage.
- Entertainingly Wrong: One of the gorillas refers to the entire Justice League members as humans, including J’onn and Hawkgirl. While Hawkgirl could pass off as a human aside from her wings, J’onn clearly can’t. Apparently, by isolating themselves from the outside world, the citizens of Gorilla City have remained ignorant about events such as the recent alien invasion.
- Everyone Has Standards: Those directly involved in Grodd's defeat feel like being reduced to a vegetative state is too harsh of a punishment for him. Green Lantern admits he's close to pitying him while Solovar promises the league he will be properly cared for.
- Hidden Depths: The Flash's intuitiveness is commented on by a surprised Green Lantern.
- Innocuously Important Episode: The introduction of Grodd and Flash frying his brain will have repercussions in Season Two ("The Secret Society") and especially Season Five. The Bruce/Diana flirtation really begins with this episode and will run through Season Three. Finally, on a Meta level, this episode was writer Dwawne McDuffie's first (albeit freelance) contribution to the series. Bruce Timm was so impressed with the teleplay that McDuffie was invited back for more episodes (and eventually became a Story Editor, Producer, and a defining creator in the DCAU's closing years).
- I Take Offense to That Last One:Gorilla Grodd: Humans are slow, ugly, immoral, and have an unpleasant body odor!
Flash: Hey, who you calling slow? - Ink-Suit Actor: The African American Central City police detective who interrogates Flash as the "bad cop" bears a passing resemblance to his voice actor Bill Duke.
- Interspecies Romance: Grodd and Corwin.
- It Works Better with Bullets: This is how Flash defeats Grodd.
- Lame Comeback: Flash to Grodd: "Oh yeah? Well, you're...naked!" He actually shrugs to Solovar behind him because he knew it was lame.
- Let's Fight Like Gentlemen: Flash challenges Grodd to a fair-fight where he won't use his Super-Speed if Grodd stops using his mind-control, even daring him to take off his helmet while taking off his own protective headband. However, Flash knew that Grodd wouldn't honor this, and it was all part of his plan to trick Grodd into frying his own brain since he already sabotaged his helmet earlier in the fight.
- Lost World: Gorilla City is this trope.
- Mass Hypnosis: Gorilla Grodd controls the populace of Central City with his mind-control helmet as part of his Evil Plan.
- Mistaken for Spies: The gorillas of Gorilla City mistake the Justice League for spies from the outside world, leading to them capturing and interrogating them, with them not believing them when they constantly say they aren't spies.
- Mythology Gag:
- Flash's hallucination sequence features several references to various covers of different Flash/Barry Allen comics.
- The "good cop" interrogating Flash looks like Barry.
- Not Brainwashed: Dr. Sarah Corwin. The Flash assumes she was being controlled by Grodd just like everyone else was, but she reveals that she was actually a willing accomplice.
- Omnicidal Maniac: Grodd, as always.
- One-Shot Character: Dr. Sarah Corwin appeared only in this episode.
- Play-Along Prisoner: Flash submits to being arrested for the theft of radioactive isotopes (which he did under Grodd's mind control). When Green Lantern arrives to bail him out, he points out that there's no way the police could have arrested him had he actually wanted to escape. Flash then proves it by handing the police interrogating him the handcuffs that had been on his wrists a few moments prior.
- Present Company Excluded: When Green Lantern suggests calling for backup from the rest of the League to help with Grodd, Flash asks him if the two of them cannot take down a dumb gorilla, quickly adding "No offense" to Solovar, who was with them.
- Ship Tease: This two-parter episode marked the first indisputable example for Batman and Wonder Woman, where he desperately tries to dig her out of the rubble while calling out her name, and her pecking him on the cheek in gratitude when she notices his dirty hands. Interestingly,
Word of God is that it was originally written as concern for a friend. However, after the fanbase latched onto it, Bruce Timm decided to amp up later moments (despite the Foregone Conclusion that is Batman Beyond). - Self-Restraint: Shown by Flash after he's arrested; as Green Lantern tells the police, they could never have held him with a pair of handcuffs had he wanted to escape.
- Shout-Out:
- Solovar's first words to the Flash: "Get your stinking paws off me, you filthy human!"
- Flash calls Solovar "Mojo".
- At the court where Grodd is making his big speech, Flash heckles him to "go climb a skyscraper".
- Smile of Approval: One of the gorillas who accused the heroes of being spies gives a smile at them for stopping the missiles from destroying Gorilla City.
- Smug Super: Flash is boastful of his accomplishments while trying to woo a couple of women. They are less than impressed, at least until he swings into action when a wildly swerving truck almost gets them hurt.
- Turn the Other Cheek: Batman, Wonder Woman, Hawkgirl, and J'onn instantly forgive the gorillas for falsely imprisoning them and interrogating them, volunteering to help save them from Grodd's missiles. This in turn earns them the respect of the gorillas, who apologize for how they treated them.
- Villainous Breakdown: It's subtle, but when the second missile has been de-activated, the normally smug Grodd starts to lose his composure. By the time the final missile is done for, he's visibly seething, saying he'll rip Flash limb-from-limb, and rather than tactically retreat or try to escape, he demands Flash stand still and fight him. It works against him, if he'd given the matter more careful thought, he might've realized even Flash would not be stupid enough to take off his protective headband.
- You Watch Too Much X: This exchange:Flash: Usually, when a city looks this empty, flesh-eating zombies are involved.
Green Lantern: You watch too many movies.
Solovar: Shh! Listen.
(sound of a crowd chanting Grodd's name)
Flash: Maybe you don't watch enough.
