Una banda de espías industriales liderada por un hombre llamado Michael Lee mata a todo un equipo de agentes del Servicio Nacional de Inteligencia. Dong Gwan Su se convierte en el nuevo líder del Equipo de Seguridad Industrial 3 y debe reunir un grupo de agentes. Sin embargo, sus opciones son limitadas y con las órdenes del subdirector, tiene que llevar a bordo a un agente excéntrico. Se revela la historia de cómo Chan Mi terminó cargando con la culpa por perder a Michael Lee e ir a prisión. Hace tres años, en plena operación para atrapar a Michael, Ye Eun da a luz a su bebé sola. Tanto Chan Mi como Mi Soon sufren un golpe cuando pierden a un compañero de equipo. Ahora las tres mujeres deben unirse para atrapar a Michael de una vez por todas.

Chan Mi, Mi Soon, y Ye Eun reciben sus nuevas asignaciones. Sin embargo, antes de que puedan acercarse a sus objetivos, deben infiltrarse en Il Kwang Hitech siendo contratados como empleados. Mientras tanto, Ye Eun lucha por adaptarse a trabajar en el campo. Preocupada por su hija, sigue cometiendo errores en el trabajo. Ye Eun debe hablar con su objetivo de celebridad, Woo Won, y convencerlo de renovar su contrato con Il Kwang Hitech, pero ella lo estropea tremendamente. Mientras tanto, Chan Mi entra en la oficina del CEO Yoon Seok Ho y Mi Soon se cuela en el centro de investigación de Il Kwang para instalar una cámara. Sin embargo, ambos terminan atascados en el lugar.

Chan Mi y Mi Soon deben escapar de la oficina del Director General y del Jefe de Investigación antes de que los atrapen. Chan Mi se las arregla para salir, pero se da cuenta de que olvidó traer el pendrive. Cuando vuelve a entrar, Seok Ho la ve y comienza una conversación. Mientras tanto, Ye Eun y Chan Mi van al centro de investigación para rescatar a Mi Soon. El equipo finalmente escapa de su primera misión, pero el Jefe Tak Sang Gi tiene sospechas sobre la nueva secretaria de Seok Ho y comienza a investigar. Mientras tanto, el gerente de Woo Won recibe una llamada para entregar el paquete que fue sacado de contrabando del centro de investigación de Il Kwang. Mientras Chan Mi y Seok Ho almuerzan juntos en la cafetería de la empresa, Sang Gi se les acerca.

Mientras Ye Eun va a la casa de Woo Won para convencerlo de renovar su contrato de modelaje con Il Kwang Hitech, Chan Mi y Mi Soon rastrean a Tak Sang Gi a un club. Las cosas no salen como se planeó, como siempre. Mientras tanto, el manager de Woo Won, Cheol Woong, huye después de plantar un objeto importante en el lugar de Woo Won. Mientras trata de hackear el sistema de seguridad de Woo Won, Ye Eun ve una sombra sospechosa acechando. Antes de que se den cuenta, ambos están atados en el maletero de un auto. Ye Eun usa su dispositivo de rastreo para señalar un Código Azul y el resto del equipo se apresura a salvarla. ¿El equipo será capaz de salir de esto sano y salvo?

Gwan Su recibe un disparo mientras el equipo va a salvar a Ye Eun, pero por suerte está bien. Mientras tanto, Chan Mi persigue a la secretaria de Tak Sang Gi, Koo Tae Rim, en una motocicleta. Mi Soon y Ye Eun siguen en la camioneta y arrestan al Secretario Koo. Con la información que obtienen del interrogatorio, el equipo se dirige al aeropuerto. El equipo toma un vuelo con destino a Taiwán persiguiendo a Pi Cheol Woong, el antiguo manager de Woo Won que robó un chip con información de Il Kwang Hitech. Chan Mi se disfraza como una pasajera embarazada mientras Mi Soon entra como asistente de vuelo. Mientras tanto, Ye Eun debe atender los caprichos de Woo Won, que es más exigente que nunca.

Part 1: The team flies back to Korea with Pi Cheol Woong in handcuffs. They put on an act to scare him into telling them about his orders. The team prepares to lure and capture Wang Kai when he comes to Korea to pick up the package. Meanwhile, Ye Eun must look after Woo Won, who experiences a severe allergic reaction on the plane. Part 2: The team prepares for their show down with Wang Kai’s men and gets Pi Cheol Woong to cooperate. Meanwhile, Ok Cheol takes charge of the operation under Director Myeong’s orders and he is eager to do a better job than Tak Sang Gi. The operation begins, but right from the start, Chan Mi, Ye Eun, and Mi Soon walk into an unexpected dangerous situation.

Part 1: The team manages to get out alive from the explosion, but their key suspect dies. Pi Cheol Woong ends up in the hospital after the traumatic incident, leaving the team without any good leads. While getting an earful about the operation going south from Chief Seo, Gwan Su states that he suspects someone is leaking information from inside the NIS. Part 2: Gwan Su and Mu Hyeok get a new lead on Michael’s whereabouts and call the rest of the team to a hotel. Chan Mi does not respond to the call but ends up running into Mi Soon at the hotel. However, Ok Cheol gets a text message from Michael, letting him know that the NIS is on to him. Mi Soon goes back into Il Kwang’s lab to get Michael’s contact information.

Part 1: Michael’s phone number leads back to an unexpected person and Ok Cheol uses his computer to reverse hack Ye Eun’s laptop. Now that Michael’s people know that Chan Mi and the team are from the NIS, Chan Mi starts to notice that she is being followed by mysterious men. Meanwhile, she must drive Seok Ho to an unofficial business trip. Part 2: Chan Mi and Seok Ho go to his father’s grave together and Chan Mi realizes that Chairman Yoon’s death must have something to do with Michael as well. Meanwhile, Ye Eun gets called to Woo Won’s house to cook for him and she gets fed up with his antics. Both Chan Mi and Ye Eun come face to face with the mysterious men who are tailing them.

Part 1: Ye Eun gets asked to report to a mysterious someone about the team’s activities while Chan Mi realizes that the man following her is also an agent at the NIS. Meanwhile, Tak Sang Gi contacts Director Myeong and threatens to tell the world his secrets unless he receives a large sum of money. Later on, someone breaks into Pi Cheol Woong’s hospital room. Part 2: Seok Ho and Chief Secretary Byun plan to steal Director Myeong’s hidden ledgers. Meanwhile, Chan Mi’s suspicions on Chief Seo grows as she realizes that he sent the agent to follow her to Busan. The team is about to get disbanded after Pi Cheol Woong’s death and Chan Mi suggests to her teammates that they trust an unlikely figure.

Part 1: The NIS begins to take away the team’s equipment and access to the network. Without the support of the NIS, the team decides to find a way into Director Myeong’s office to find the secret ledger. Meanwhile, Chan Mi follows Seok Ho on an inspection tour of a construction site where she runs into an unexpected obstacle. Part 2: Seok Ho’s suspicion that his new secretary is actually the same person as his old tutor continues to grow as they spend more time together alone. However, Seok Ho’s ex-wife pays another visit and lets Chan Mi know that she has figured out Chan Mi’s real identity. Meanwhile, the team begins the operation to break into Director Myeong’s office.

Part 1: Chan Mi goes off to meet Tak Sang Gi on her own where Michael suddenly appears and kills Tak Sang Gi. Ye Eun and the team quickly trace Chan Mi's car and arrive on the scene. However, Chan Mi ends up getting shot. Meanwhile, Seok Ho finds out that Chan Mi is in the hospital and rushes over. Part 2: While stuck in the interrogation room, Chief Seo tries to use his connections to get himself out of trouble, but to no avail. Director Myeong orders Ok Cheol to take Chief Seo out. Meanwhile, Mi Soon goes to her daughter’s school to find out that she hasn’t been a good enough mom. Then, she gets a phone call about Chan Mi’s condition.

Chan Mi checks herself out of the hospital despite everyone's best efforts to stop her. Meanwhile, Woo Won hears about Ye Eun getting fired over his contract annulment and goes to Il Kwang to help her. Later on, Seok Ho and Secretary Byun get in trouble while tailing Director Myeong. When Chan Mi comes to the rescue, Seok Ho suggests that they start working together.

Chan Mi and the team finally arrest Director Myeong, but they lose Chief Seo in the process. Meanwhile, Mi Soon goes to her daughter's school to talk to the bullies' mothers. However, when they refuse to admit that their kids were in the wrong, Chan Mi and Ye Eun step up to help put a stop to the bullying. The team also figures out who Michael is.

Michael turns out to be Ok Cheol, the head of research at Il Kwang's Research Center. The team follows Ok Cheol and Wang Kai to Jeju Island to stop their next transaction. Meanwhile, Seok Ho finds himself at risk of losing his position as the CEO of Il Kwang Hitech and voluntarily goes to the prosecution for questioning.'

Chan Mi saves Mi Soon and Ye Eun from Wang Kai. Meanwhile, Secretary Byun arrives in Jeju and chases Michael down. He succeeds in taking the chip away from Michael but ends up getting hurt. The operation comes to a close and six months go by. Chan Mi finds herself face to face with Seok Ho and her team once again.