1x49 - The Centurions

Jake has Crystal beam Ace back up to Skyvault, freeing him from the squid's clutches. Naro tells Jake and Sean that he intends to use the probe to take over Atlantis, and O'Connor agrees to help him. Meanwhile, Max and the two from Sealab escape from their confinement and look for a transmitter, but are stopped by Diana troops. Ace returns to Sealab, which engages its new force field to descend to Atlantis' depth. Max and the others escape from Atlantis and take Diana with them, but they are soon attacked by Naro's forces. Sean uses the Venus Probe to return to Sealab, where it is soon boarded by Naro and his followers. Jake escapes and beams outside Sealab, where he attempts to get on board. Sean reveals to Ace that he's still really on their side, and together they attempt to regain control of the base. Now working with Diana, Max and the rest of the Centurions try to defeat Naro's forces. Science Lesson: Uranus by Ace.