Police detective Kang Mi-seon leads a life filled with the chaos of her work involving frequent drug busts alongside her police squad. Meanwhile, her househusband, Kang-moo (played by Hwang Jung-min), finds himself reconnecting with an old colleague, Hee-joo (portrayed by Hye-jin Jeon), to seek information about their missing colleague, Joong-san (played by Kim Joo-hun). However, their casual meeting takes a turn when other detectives misinterpret the situation, leading them to believe that Kang-moo is having an extramarital affair. This rumor reaches Mi-seon, who later discovers photos of her husband with Hee-joo, leaving her feeling betrayed and suspicious.
The plot unfolds further, taking us to a flashback set in Russia six years prior, where Kang-moo and other South Korean defense personnel attempt to stop a ship suspected of collaborating with North Korea. To their shock, they realize the vessel is, in fact, operating under South Korean orders. During the operation, Kang-moo is captured and tortured to reveal a vital passcode, which he divulges selflessly to save a colleague, but at the cost of his career in law enforcement.
Returning to the present, Mi-seon, overwhelmed by doubts, begins to follow Kang-moo, ultimately witnessing him with Hee-joo in a hotel room. Desperate to confront them, she grabs a taser, but her boss urges her to consider the entire situation before resorting to violence. In a bid to uncover the truth, Mi-seon collects fingerprints from a car Hee-joo had touched, leading her to identify her, and discreetly installs a tracking device on her husband’s phone to monitor his locations. She learns of a peculiar "H" emblem linked to a treacherous South Korean military unit.
In a daring move, Kang-moo dons the disguise of a construction worker to infiltrate the military unit's hideout and liberates a prisoner. Once safe in a hospital, the prisoner shares a secret code with Kang-moo, but their conversation is compromised when the traitors discover it through hidden cameras. With imminent danger, Kang-moo receives a warning from the prisoner, only to feel helpless when he learns of the prisoner's subsequent murder, compounded by his own injuries caused by an army truck.
In another twist, Mi-seon visits a safe house where Kang-moo was previously located, spotting a thief in the act of stealing a USB stick. She swiftly intervenes, copying its data to her phone and sending it to her husband before destroying the drive in a bid to eliminate evidence. However, during her captivity, she is tortured but resolutely reveals the location of the files. In a brilliant moment of collaboration, Kang-moo manages to escape his own confinement and races to rescue Mi-seon. They make their getaway in a truck, marking a turning point in their relationship as Kang-moo admits to being a special agent. The couple enters a safe house, arming themselves for what lies ahead.
Now united, Kang-moo and Mi-seon storm the headquarters of the traitorous military unit, facing off against guards and managing to reset the computer systems just as illicit funds are scheduled to be shifted. The situation escalates when Hee-joo attempts to flee in a vehicle, only to be cornered by Mi-seon. Ultimately, the husband and wife duo successfully seize a briefcase full of money and turn it over to the South Korean army, thwarting the treachery.
Fast forward six months, and the couple has found a sense of peace in a safe house, where they embrace their lives as partners, working together to take down drug operations, reveling in their newfound harmony despite the earlier chaos and deception.
