Yugi, Joey, Téa, Tristan and Bakura were trapped in the island underground after Bandit Keith had Bonz, Sid and Zygor push a boulder in front of the entrance they used. Searching for another way out, they found the dungeon.
In the dungeon, they were confronted by Para and Dox, who imposed a Team Duel and a riddle, which Yami Yugi and Joey would need to win and answer correctly in order to exit. The Duel was a Labyrinth Duel, which Yami and Joey managed to win.
In the riddle the Paradox Brothers claimed that one of them would only tell the truth, while the other would only lie and one of them guarded the door that led to the exit. Yami and Joey were permitted to ask them one question each. Joey thought he figured the riddle out and asked the brothers to point to the door they were guarding to determine the liar. However Yami suspected the brothers were being sneaky, since neither spoke while pointing to their doors and there was a possibility that both were liars. He suspected they would say whichever door he choose was incorrect, so he tricked them into thinking he had chosen one door and revealed he had really chosen the other after they said the first was incorrect.
In the manga, as the group left the cave, they noticed that both doors led to the same place.