The Deucalion has crashed after the Aldnoah drive stops working and the crew scrambles to find Princess Asseylum. Slaine learns the history of Mars and is given an ultimatum by Count Saazbaum. 
The Deucalion flies over Siberia, but it's Aldnoah Drives stops suddenly, as Captain Magbaredge reports. Eddelrittuo says that shouldn't be possible so long as she lives, Inaho suspects something has happened to Seylum and asks where she is.
Kisaki reports to XO Mizusaki that damage to the hull is negligible and that departmental damage checks are underway. They are currently operating on auxiliary power. Nina comments that it was a good thing that they were flying at a low altitude; their gravity field was churning up the snow, and that seems to have acted as a shock absorber. XO Mizusaki orders the crew to launch their Kats and put them on the watch. Repairs should be made to any damaged areas ASAP. She orders the engine room to inspect the Aldnoah drive and determine the cause of the shutdown. Just as she wonders where the Captain is, the Captain orders her to send medics immediately.
In the showers, Inaho cannot find any signs of breathing or pulse on Princess Asseylum, so he attempts CPR. He will use the defibrillator, so he asks Eddelrittuo for towers to dry off the Princess. The Captain hands Eddelrittuo one. Warrant Officer Kaizuka, Lt. Marito, and Dr. Yagarai rush through the Deucalion with medical supplies. Inaho sets the countershock to 200 joules. Inaho continues to perform CPR. Eddelrittuo wants help, but Inho says she is too light. The Captain compliments Inaho for thinking fast, but Inaho says he learns this in school. The Captain says students never take CPR seriously, all they do is giggle about the mouth-to-mouth. Inaho says that could save a life and proceeds with mouth-to-mouth to revive the Princess. He blows into her mouth, but with no signs of consciousness, he goes back to pumping her chest. Eddelrittuo tears up, fearing for her friend. The Captain volunteers to take over, but Inaho says he can handle it.
Inaho tries mouth-to-mouth resuscitation again, and it works. He pulls away as the Princess opens her eyes and coughs repeatedly. Everyone wonders what had happened. The Princess says she was attacked by "her". Suddenly, Rayet comes from the corner and grabs the Captain's gun and points it at her. Dr. Yagarai and the others arrive, and he asks where the patient is. Rayet tells them to get back and fires a warning shot at the ceiling. Dr. Yagarai and the others back out as Rayet points the gun at the Captain. Rayet reveals that she is a Versian, or a Martian, as she corrects herself. She explains that the assassination was led by her father, a Martian spy living on Earth. He was promised a title and a reward if he killed the Princess. But when her father completed his mission, he was put down like a dog, to be silenced.
She can't go back to being a Martian, but she is not a Terran either. She blames all that has happened on the Princess; the death of her father, the start of the Second Earth-Mars War, the betrayal, and her own loneliness are because the Princess came here. The Princess stands up from behind her shower cubicle and apologizes to Rayet, she approaches Rayet at gunpoint. Rayet is both angry and confused and tries to fire at the Princess, who has fallen to her knees. Hearing gunshots, Warrant Officer Yuki opens the door and aims her gun at Rayet. Rayet raises the gun to her own head. Luckily, Inaho quickly throws Rayet to the floor and points the gun in a safe direction. Inaho couldn't care less if she were a Terran or a Martian because she hates their enemies, trying to kill her. Still, most importantly, she has fought at their side. Rayet stands up and gives the Captain her gun back, who orders Warrant Officer Kaizuka to take Rayet into custody.
The Princess lies in the infirmary, recovering from the incident. She holds up Slaine's pendant. Dr. Yagarai asks if it is a Martian trinket, but she says she has been told that it is a Terran good luck charm. The Captain asks for the Princess' condition, the Princess volunteers to reactivate the Aldnoah drive despite her condition. Afterward, Dr. Yagarai gives the Captain, Lt. Marito's patient file on a disc.Warrant Officer Kaizuka walks into the brig. Rayet says thanks because compared to where she's been sleeping, it is paradise. The Aldnoah drive comes online again, and the Deucalion launches into the air. Later, Lt. Marito sits in the Kataphrakt Bay drinking and discussing Rayet's situation and his own while the Captain views Lt. Marito's patient file.
Slaine sits in the brig at Castle Saazbaum. Count Saazbaum walks in a shows Slaine data on Tanegashima, the island where he was retrieved. Slaine confirms he saw a ship that was most likely Aldnoah-equipped. Count Saazbaum asks if it was Princess Asseylum that activated it. Still, Slaine refuses to answer out of concern for her. Count Saazbaum shows Slaine an image of the Deucalion, the Kataphrakt belonging to Viscountess Orlane, that has gravity control capability. Viscountess Orlane was the woman who was to be Count Saazbaum's wife. Count Saazbaum explains the reasons as to why Mars is at war with Earth.
In 1999, Count Saazbaum in his Dioscuria and Viscountess Orlane in her Deucalion was sent to Tanegashim as an advance party. They believe their task of taking the planet would be easy as they both fly over the blazing ruins of Tanegashima. But powerful space-time distortion waves occur from the Hyper Gate. As Count Saazbaum looks up at the moon, he sees it being obliterated. They try to escape, but the distortions are affecting the Deucalion's anti-gravity device. Thus, she is unable to fly, just as Count Saazbaum tries to save his fiancé, a large fragment of the moon lands on her and her Deucalion.
The Deucalion reaches United Forces of Earth Headquarters in Russia. HQ grants the Deucalion docking clearance at the request of the Captain. They approach Dock #6. The UFE soldier who gave them clearance cannot believe his own two eyes. His comrade beside him says a flying battleship is like something out of a Japanese comic book. Their commanding officer says it was abandoned because the Aldnoah drive could not be activated. He deduced the ship's reports that harboring Princess Asseylum must be true. The landing lights activate for the Deucalion as it enters HQ. It descends to touchdown underground.
The refugees from Shinawara leave the Deucalion. Warrant Officer Kaizuka explains the vastness of the base to Dr. Yagarai. Calm walks over to his friends and asks Inaho why he's still using the Sleipnir. Inaho says he is used to it and that heavier armor wouldn't have helped against anything they've fought so far. Inko wonders if they have to fight since they can let the professionals do their job, but Inaho assures his friends that one can't be too careful. Inaho reads up on Kataphrakt specs on his tablet.
Inaho enters the Deucalion's Aldnoah drive room, Eddelrittuo and Princess Asseylum follow him. The Princess is very grateful for Inaho saving her life again. Still, Inaho simply says it's because they are in a war. She has lost track of how many times he has saved her. The Princess rhetorically asks Inho if he is a kind person who mildly frustrates Eddelrittuo, and wonders if they will still be friends after the war is over, Inaho says yes.
Afterward, Princess Asseylum broadcasts a speech all over the base, a call to end all hostilities and the truth of who assassinated her; the Orbital Knights. Count Saazbaum observes this broadcast from his own Landing Castle. Count Saazbaum takes Slaine to see Count Cruhteo's Kataphrakt, the Tharsis, whom Saazbaum considered unworthy of piloting. Count Saazbaum says Princess Asseylum's location has been pinpointed via laser transmission to the Moon base. It is under the control of those who feel as he does and thus the transmission to call for a cease-fire would not be heard of on Mars.The final battle is about to take place. Count Saazbaum suddenly shoots the handcuffs off of Slaine's hands, stating that the debt to Slaine's father has been paid and offers Slaine the choice to join his own forces or flee to Earth. Castle Saazbaum descends upon United Earth HQ, against the wishes of the Princess.
|“|| Darzana: You think fast on your feet.
Inaho: We learn this in school.
Darzana: Students never take it seriously. All they do is giggle about the mouth-to-mouth.
Inaho: It could save a life.
|“|| Who are you? |
A Versian - No, a Martian.
—Rayet Areash reveals her identity and motive to her hostages
|“|| What are you doing? |
Automatics wont’ fire with the slide open. I thought this was the best way to stop you without it discharging accidentally.
—Inaho prevents Rayet’s suicide
|“|| Deucalion |
A Kataphrakt belonging to Viscountess Orlane that has gravity capability.