Actor So Ji-sub's action drama "Agent Kim Reactivated" surpassed the 20 percent viewership mark just four episodes into its run. According to ratings tracker Nielsen Korea on Sunday, the fourth episode of the SBS Friday-Saturday drama, recorded a nationwide rating of 21.6 percent on Saturday. That makes it the third-highest-rated SBS Friday-Saturday drama in history, trailing only "The Penthouse 2," which hit 29.2 percent, and "The Fiery Priest,” which reached 22 percent. The show has climbed steadily since its premiere. It opened with 9.5 percent, jumped to 15.7 percent in the second episode, reached 18.8 percent in the third and broke 20 percent by the fourth episode. The series, which premiered on June 26, follows Kim (So Ji-sub), a former special agent, who now lives a quiet life as a worker at a small bank. The change in job was the last wish of his late wife, who asked him to "just live as a father." However, when his only daughter Min-ji (Seo Su-min) is kidnapped, he draws on his deadly fighting skills to save her. In the fourth episode, Kim teams up with his old friends Seong Ha