The Age of Shadows

Kim Jang-ok and Joo Dong-sung, members of the Korean independence group Heroic Corps, visit the wealthy Kim Hwang-sub under the pretense of securing military funds, but it's a trap. Surrounded by Japanese forces, Kim Jang-ok fights valiantly in a gun battle but ultimately takes his own life when confronted by his former friend Lee Jung-chool, now working for the Japanese police. Lee, however, quietly releases Joo Dong-sung, arousing suspicion among fellow Heroic Corps members. Internal distrust peaks when Jo Hwe-ryung accuses Joo of being a traitor, but Kim Woo-jin intervenes and banishes Joo for his compromised identity.

Following the incident, Japanese authorities order Lee Jung-chool to investigate Kim Woo-jin. Despite recognizing each other's true identities, Lee and Kim feign friendship. Meanwhile, Lee is assigned a partner, Hashimoto, whose real task is to monitor Lee himself. As surveillance intensifies, Lee attempts to protect the Heroic Corps by delaying Hashimoto's actions, but the group narrowly escapes to Shanghai. In Shanghai, Heroic Corps leader Jung Chae-san and Kim Woo-jin recruit Lee to assist their cause. Lee ultimately agrees to help smuggle explosives back to Korea, shifting loyalties under increasing pressure.

Back in Korea, Lee warns Kim Woo-jin that a spy is among them. Kim devises a trap by feeding different rendezvous times to each member to expose the mole. When the leak confirms the spy's identity, it is revealed to be Jo Hwe-ryung. In a tense confrontation aboard a train, Kim executes him in the name of the Heroic Corps. As the group arrives in Keijō (Seoul), chaos erupts when police confront them. Yeon Gye-soon kills officers attempting to arrest her, triggering a shootout where most of the resistance members die or are captured. Kim escapes with help, managing to smuggle in the explosives.

Lee, under suspicion, is ordered to find Kim and tortures Gye-soon to maintain his cover. Eventually, Lee is tricked by Joo Dong-sung and leads authorities to Kim's hideout. Kim is captured after a desperate escape attempt. To avoid revealing secrets under torture, Kim bites off his own tongue. Lee is also arrested but feigns loyalty to the Japanese to receive a light sentence. During the trial, Lee tearfully insists he was never aligned with the resistance, honoring Kim's earlier request to act as a non-affiliate so their mission could continue.

After release, Lee learns of Gye-soon's death and receives word of a party hosted by Japanese collaborators. Remembering Kim's final wish that at least one person survive to complete their mission, Lee plants explosives at the event. Simultaneously, a Heroic Corps operative assassinates Joo Dong-sung. The bomb detonates, killing high-ranking officials including Higashi. Back in prison, a mute Kim Woo-jin hears of the mission's success and smiles in relief, his sacrifice having meaning. Lee later finds Kim Hwang-sub, whose betrayal led to Kim Jang-ok's death, and kills him to avenge his friend.

On August 3, 2015, it was announced that Warner Bros. would finance and distribute its first ever Korean-language 1930s set drama Secret Agent, and the $8.62 million budgeted film would also be produced by Grimm Pictures.^[11] The project and script was developed by Lee Ji-min and Park Jong-dae, which Kim Jee-woon would direct and the cast would be Song Kang-ho and Gong Yoo.^[11] A trailer was released on July 14, 2016, revealing the new title as The Age of Shadows.^[12]

• Assassination, a 2015 South Korean film with similar topic and background
• List of submissions to the 89th Academy Awards for Best Foreign Language Film
• List of South Korean submissions for the Academy Award for Best Foreign Language Film