Terra Incognita Part One is the first episode of 3Below.
A blond teenage girl nervously steps onto a stage as the spotlight focuses on her and an audience applauds. After some microphone feedback, she introduces herself as Aja Tarron of House Tarron. Reading from a paper, Aja begins to tell a story that begins on a faraway planet called Akiridion-5.
Two colorful alien creatures fiercely butt heads and fight as it pans to show a variety of Akiridion children watching the battle. They clamor excitedly and make bets on which one will win only for another bigger creature to crush both bugs under its feet while running away, much to their irritation. A cape-donned Aja pursues her pet dog, Luug, all while complaining angrily.
It is Coronation Day on Akiridion-5 and King Fialkov and Queen Coranda wave to a vast audience while wondering where their daughter, Aja, has run off to. They are irritated to learn from their advisor that she is yet again trying to run away. Their son, Krel Tarron, is contacted by his older sister; Aja confesses that she won't attend the ceremony as she is uninterested in becoming queen-in-waiting. Krel lectures her before she ends the call to keep chasing Luug. Krel expresses his insecurities about becoming king-in-waiting when his father confronts him about Aja. King Fialkov encourages him to accept his role in stride with the knowledge that his sister will always be by his side, even when his parents are not. Lieutenant Zadra urges her king to start the ceremony and they have no choice but to go ahead without Aja.
Meanwhile, after flipping off of buildings and avoiding many vehicles and Akiridion citizens, Aja finally catches her dog. She tackles him and yanks her serrator from his mouth, scolding him for playing with her belongings. At the ceremony, Queen Coranda announces the joining of two divided houses, House Akraohm and House Ventis of her and her husband's ancestors, respectively, into House Tarron and Krel is marked as a worthy heir to the throne. As per tradition, the king-in-waiting is to provide a demonstration of combat for all to see; Commander Varvatos Vex is chosen as Krel's combatant. Their fight begins with Varvatos Vex getting the upper hand until Krel uses one of his handy inventions to imprison the Commander into a sphere. Varvatos uses his serrator to escape and pummels him, prompting Krel to strike him for the first time. King Fialkov dismisses Varvatos in order to spare with his own son, also per tradition.
Before they can duel, the shield enclosing the planet is shot at repeatedly. Queen Coranda realizes that the strikers belong to the exiled traitor, General Morando just as his ship comes into view. The royals and their subjects quickly evacuate and the king and queen order Krel to accompany Varvatos and Zadra in finding Aja. The shield is all of a sudden disabled, much to everyones shock, and Zadra deduces that there is a traitor among them.
Aja takes Luug and flees with the other citizens as Morando's fleet starts to attack the city. The princess stops fleeing in order to rescue a young child from falling rubble and reunite her with her mother. Her selfless action backfires as she is attacked while protecting the family but Varvatos saves her in the nick of time and she joins him in his aircraft before Krel calls from Zadra's ship to explain the situation. Zadra's ship is damaged by Morando's forces yet Krel is able to reroute power quickly, saving them both. The four of them bring down Morando's ships before retreating to the royal palace.
At the palace, Morando leads his Taylon Phalanx army against the king and queen. He has returned from exile and intends to claim the throne as his own. The royals lead their army to battle against him although they are eventually outnumbered and forced to retreat into the palace, where they reunite with their children. With the Taylon no longer loyal to House Tarron nor Akiridion-5, the planet is deemed unsafe and the royals are urged to flee. As they escape to the Mothership, Morando infiltrates the palace with his army in tow. The royals refuse to surrender to him and attempt a last effort to fight him off but Morando attacks them both, much to Varvatos Vex's horror. Before retreating into his core, King Fialkov entrust Varvatos with the protection of his children, which the warrior solemnly accepts.
Vartavos takes the royal cores and retreats with Zada and the royal children to Mothership. As Morando's tropes surround them, Zadra heroically stays behind to fight off their enemies and buy the trio more time to jumpstart Mother. Despite Morando's attempts at grounding them, Aja and Krel manage to flee the planet with their guardian. During the escape, Aja begs Mother to save her parents and the ship places their cores into stasis although with an unknown completion time. Heartbroken, Aja recalls a time where her mother counseled her after one of her runaway attempts went awry. Krel comforts his sister as she grieves their parents downfall and urges her not to blame herself for what happened.
Varvatos demands that Mother should find a planet for them to seek refuge where Morando will never suspect to find them. Mother finds two suitable planets for his description: one that is about to be sucked into a black hole, quickly rejected by Krel, and one that inhabitants named after dirt, the planet Earth. Aja quickly warms up to the idea, hoping to find adventure there.
Down on Earth in Arcadia Oaks, an unsuspecting Eli Pepperjack rides his bike through the neighborhood, delivering newspapers to doorsteps. He happens to look up at the sky right as the Mothership enters the atmosphere. Distracted, he accidentally crashes into a fire hydrant.
Heavily damaged by Morando's attacks, Mother crash-lands into a nearby forest, skidding to a halt alongside some houses in the small town. Varvatos and the teenagers are miraculously unharmed. Seeing that none of their other systems work, Mother is camouflaged to resemble an outdated household right at Eli pulls up in front of them, innocently hoping to interest the family inside with a newspaper subscription. Eli's insistence urges the Akiridians to disguise themselves as primitive humans in order to blend in with the local citizens. Mother choses the following forms for Aja, Krel, and Varvatos, respectively: a girl, a Latino, and a senior citizen. When they open the door to greet Eli, they resemble ordinary humans, only Varvatos immediately threatens to kill the boy.
Aja continues her narration, concluding that Morando's plans had gone just as awry as theirs.
- Tatiana Maslany as Aja Tarron/Queen Coranda
- Diego Luna as Krel Tarron
- Nick Offerman as Varvatos Vex
- Glenn Close as Mothership
- Alon Abutbul as General Morando
- Hayley Atwell as Zadra
- Andy Garcia as King Fialkov
- Jennifer Hale as Izita
- Chris Obi as Loth Saborian
- Cole Sand as Eli Pepperjack
- Frank Welker as Luug
- Goof: The episode shows the ship crash-land in Arcadia at dawn, whereas in the Trollhunters episode "Night Patroll", the ship is seen landing at night.
- Eli's voice becomes much deeper, starting with this episode (understandable, as his voice actor, Cole Sand, has further matured since starring in Trollhunters).
- This is lampshaded by Eli himself, as well as Steve Palchuk in the later episode "Party Crashers" when Eli implores Steve to "Listen to [Eli's] voice, Steve. I've matured. And mature people go into the woods and hunt the legendary Arcadian Billycraggle." Steve rebukes with "Hush your manly voice!" so that Eli doesn't blow their cover as Creepslayerz.
- Queen Coranda's first lines of the series "Smile and wave. Smile and wave." could be an allusion to the line "Just smile and wave, boys. Smile and wave." uttered by Skipper in the DreamWorks animated film Madagascar.