In the penultimate episode of Tempest, Ok-seon steers Mun-ju to one of her vessels, where she orders her henchmen to initiate a beating upon the latter's arrival. She then informs Jun-sang that she has accomplished everything for him, including the heinous act of murdering Jun-ik.
As the scene shifts, we find Mun-ju being escorted to Ok-seon's quarters. There, she delves into her past: her journey from being sent to the US with her husband, where she discovered her talent for socializing and using secrets to wield power. Her trajectory as a CIA operative eventually led her to become an arms dealer, igniting a passion for weapons and a dream of creating a submarine equipped with missiles.
Ok-seon shares how she used her connections in North Korea to procure new weapons and secretly sold them to other countries. She even coaxed the Idishian king into acquiring a nuclear submarine to project power.
Meanwhile, San-ho drives his car into Director Yoo's residence, straps him to a bomb, and even blows up Yoo's house to send a clear message of his intentions. Holding Yoo hostage, San-ho demands a minute with President Chae. When she arrives, he releases Yoo and in a poignant moment, reminds President Chae of 13th August 2007, the day when she and Mun-ju brokered an agreement between four nations. He also references Proust, a subtle code that President Chae deciphers, signaling San-ho's message.
After their brief encounter, San-ho allows the police to cuff him while Yoo informs him that his grandmother passed away two days ago. Alone with President Chae, San-ho updates her on the submarine's status, and she speaks with the US President, subsequently having Director Yoo arrested for framing Mun-ju as a spy.
Back on the ship, Ok-seon unveils a device that allows her to launch the missiles herself, making it appear as if Idishia is responsible. In the US, Anderson speaks with Camilla and requests her to freeze the accounts funding the submarine. However, his call is interrupted by the arrival of US officers who arrest him. As he gets a chance to speak with President Hauser, he explains the situation and asks for the Idishian funds to be frozen.
Jun-sang steps in to assist Mun-ju in a dramatic fashion, as if he were a knight in shining armor, resolving the immediate crisis. The Aseom Shipping employees' accounts being frozen serve as a harbinger of things to come. Meanwhile, Mun-ju's revelation about Jun-ik's knowledge of Ok-seon's true parentage and her troubled childhood in North Korea adds depth to the story. Ok-seon's actions are now seen through the lens of trauma, but her belief in the power of her button to bring about peace by preventing the US from starting wars elsewhere is a testament to her idealism.
As Jun-sang enters the room with an arrest warrant for Ok-seon, it becomes clear that he has been diligent in his efforts to gather evidence against her while in Germany. However, their predicament on the boat complicates matters. Ok-seon's men give chase, and Jun-sang and Mun-ju flee, with Jun-sang sustaining an injury in the process. In a moment of heroism, he passes on a card that provides direct access to Kim Han-sang, the North Korean leader.
As the coast guard's boats surround Ok-seon's ship and a fierce battle commences, the fate of the nuclear bomb hangs in the balance. Back on land, President Chae orders San-ho to retrieve Mun-ju, and together they make their way to Ok-seon's bedroom. With Kim Han-sang on the line, Mun-ju lays out Ok-seon's plan and its potential for retribution against North Korea. After deliberation, Kim Han-sang agrees to halt the submarine delivery but warns that communication will take time. He also notes that if Mun-ju can destroy Ok-seon's transmitter, her command will be thwarted.
As the government sends fighter jets after Ok-seon, she takes drastic measures by setting a timer on a bomb in the control room and making her way to the top deck to launch the missile. San-ho and Mun-ju are determined to stop her from pressing the button, but Ok-seon reveals that her death will automatically trigger the launch system in the control room, setting off the missiles in ten minutes. She throws a disc containing the only passcode into the sea before shooting herself and falling into the water.
Mun-ju and San-ho rush back to the control room, where Mun-ju calls upon Kim Han-sang for assistance. Fortunately, Kim Han-sang reaches out to the King of Idishia, who possesses another launch device with the same code. He hands it over to Mun-ju, and with this newfound hope, they are able to stop the launch. However, San-ho faces a dangerous moment when he steps on another bomb Ok-seon had set up.
In the thrilling climax of San-ho's fate, a pressure release device, set to detonate in ten minutes, hovers in the air like a time bomb. After a heart-wrenching conversation with San-ho, Mun-ju bravely leaves to sound the alarm for the others on board. The evacuation commences, but her heart is torn as she tries to return to San-ho's side. He uses his radio to plead with her, urging her not to come back and promising to protect her. She boards the lifeboats, and soon the entire ship is engulfed in flames.
However, a fleeting glimpse into the control room moments before the explosion reveals that San-ho's former position is now empty, yet he is nowhere else in the room. President Chae later informs Mun-ju that his remains have not been found, leaving her to believe he is gone but leaving his fate shrouded in ambiguity for the drama's sake.
Fast forward to the conclusion of Tempest's storyline, the US and Idishia engage in ceasefire negotiations. The charges of espionage against Mun-ju are dropped, and she is removed from her political party. President Chae informs her that the US desires her to mediate discussions with Idishia and North Korea regarding the dismantling of the submarine.
Mun-ju embarks on a journey to Washington D.C., where she even meets with Anderson in person. The meeting proceeds smoothly, and upon her return to Korea, she finds Mi-ji recovering in the hospital. Both Mi-ji and Chang-hee still urge Mun-ju to run for President, and even President Chae calls her, expressing her belief that she would make an excellent leader. Tempest Episode 9 ends with a dramatic announcement from Mun-ju as she declares her candidacy for President.
