It's All In The Cards

It's all in the Cards is the twenty-eighth episode of both Digimon Adventure and the Digimon anime series.

Summary
With no clue of what to do, the group are led by Gennai to his home, hidden at the bottom of a lake. There, they rest, and Gennai goes over the current situation - Myotismon arrived in Highton View Terrace in Tokyo, Japan. He then gives the kids ten cards with Digimon on them, nine of which can be used to open the portal in Myotismon's castle, but only in the correct order. The next day, the group leave with the cards and Izzy's laptop configured by Gennai, and they raid Myotismon's castle. With him and his best servants gone, getting to the door is easy, and the group now try to work on figuring out the order of the cards. Izzy figures out how to order them, leaving Tai to decide on one of two more cards to insert into the sequence. When Dokugumon, one of Myotismon's servants, attacks, Tai must decide quickly, and just by luck, he gets it right, opening the door and taking the group into the real world.