A submarine investigates a strange light in the Japan Trench and promptly gets caught by combat trooper Kraken. At the Takasugi residence, Seiji tries to talk Misuzu out of cooking for him but the latter says that she has to do her duty as a mother. They’re interrupted by a phone call from the TV station informing Misuzu about the attacked submarine. Despite protesting that she has the day off and wants to spend time with her son, Seiji insists that she go to work and cover the story. When she leaves, Seiji contacts Da-Garn who’s out on patrol with Tadashin and informs him of the situation. Seiji is worried that this is related to the invader’s repeated attempts to dig holes in the Earth and wonders if they’re studying the planet. Da-Garn agrees with his assessment and suggests sending the Landers to investigate. Seiji contacts the Landers and they quickly rush off to the location. Misuzu is suspicious of Seiji’s strange behavior and fears he might have fallen in with a bad crowd. Just as she contemplates going back home, Riken Alphas fly overhead and make her continue on to the TV station. Seiji spots the Riken Alphas and summons Da-Garn, who leaves a baffled Tadashin at the police station. Seiji then summons Shuttle Saber to pick them up and follow the Riken Alphas. Jet Saber and Jumbo Saber report spotting Riken Alphas over the Alps and the Amazon. Seiji wonders if this is related to the incident at the Japan Trench and orders the Sabers to follow the Riken Alphas without engaging them. As Shuttle Saber passes over the Japan Trench, Seiji contacts the Landers and asks about their situation. Drill Lander says that they’re seven thousand meters below sea level, and Mach Lander asks how much deeper do they need to go. The banter is cut short when Big Lander spots Kraken and the missing submarine. Kraken drops a drilling machine which immediately begins drilling. The Sabers report that the Riken Alphas are all heading towards the trench. Turbo Lander suggests taking out the enemy before the rest arrive, and Seiji orders them to rescue the submarine and smash the combat trooper. Mach Lander wants to charge in but Big Lander stops him and says they need a plan to rescue the submarine unscathed. Seiji wonders what the connection between the two incidents is. Up in space, Redlone watches footage of the Brave Fighters combining and praises his robot assistant for finding their weak point which is the few seconds it takes them to combine. His assistant remarks that they are currently luring all the Brave Fighters to one location so they can defeat them all at once. A soldier reports that their drilling machine discovered a planet energy reservoir, but Redlone is too preoccupied with preparing for battle to care. The Riken Alphas arrive at an urban area and start attacking, so Seiji orders Da-Garn and the Sabers to transform and fight them.
Da-Garn and the Sabers destroy the Riken Alphas just as Redlone’s ship descends upon the city and transforms into a massive robot. Seiji orders everyone to combine but Redlone tracks their movements and stops their combination with a barrage of energy blasts. Redlone announces that he developed a radar to track the very moment the Brave Fighters finish their combination, over the objections of his assistant who claims that he was the one who developed the radar. His assistant also notes that not all the Brave Fighters are gathered together but Redlone retorts that he’ll destroy them when they come to rescue their comrades. Redlone bombards the Brave Fighters from multiple cannons, machine guns and exploding saucers. Seiji tells everyone to fight back but the exploding saucers overwhelm them and block their retreat. Seiji contacts the Landers; who managed to destroy Kraken and rescue the submarine; and orders them to quickly get to the city and assist. Seiji then quickly gets the idea to have them combine before arriving at the city, much to Redlone’s shock. Redlone tries to blast Land Bison with his heavy cannon but the latter manages to dodge in time thanks to Da-Garn’s warning. At Da-Garn’s request, Land Bison dodges past Redlone’s barrage of attacks and destroys the special radar with his Land Cannon. The rest of the Brave Fighters quickly combine into Da-Garn X and Sky Saber, then destroy all the exploding saucers with Breast Earth Flash and Saber Breaker. Redlone’s assistant tells him that their ship isn’t designed to fight in the atmosphere and Redlone immediately orders the ship to retreat into space. Seiji orders the Brave Fighters to chase after the ship. Redlone thinks he has the advantage in space but Da-Garn X, Sky Saber and Land Bison join forces into one spinning energy attack that pierces the ship. Redlone’s assistant says that they must escape but Redlone is terrified of going back empty handed. His assistant says that he will be forgiven if he brings back the data they gathered on Earth’s planet energy reservoirs but he explodes before he could give Redlone the data disc. Seiji says that the Earth is safe now, but Da-Garn X says that he detected an escape craft leaving the ship before it exploded. Seiji however doesn’t think that the survivor will return. Redlone thinks he can escape to the ends of the universe but a large ship materializes in front of him and swallows his escape craft as he screams for forgiveness. Down in the Japan Trench, the drilling machine continues to operate undetected.
An action-packed episode that brings a close to the Redlone arc. In fact this episode was so focused on the action that the only supporting characters who got any screen time were Misuzu and Tadashin and even then only briefly. We also get to see all the Brave Fighters together for the first time. I give credit to Redlone for figuring out that he needs to stop the Brave Fighters from combining; which is a strategy most villains don’t even think of until much later in other shows; but he made a huge tactical blunder in not waiting until the Landers arrived before revealing his trump card. It’s also amusing to see that despite his open contempt for the Earth robots, he sure spent a lot of time watching their combination sequences over and over as noted by his poor assistant. Naturally, all of Redlone’s bravado went out the window once he realized he has to answer to a higher power for his lack of results, but what little work he did get done will still have lasting effects for the remainder of the show.