Contains spoilers for this episode and earlier episodes.
Dal-mi joins In-jae's company after recognizing their shared interest in building for the future. Over the next three years, she becomes chief executive of Cheongmyeong, a business developing self-driving cars. Noongil gains support beyond its original team, and Won-deok gives up her food truck as her eyesight worsens. In America, Do-san, Chul-san and Yong-san enjoy professional success, but Do-san remains absorbed in work while his friends document their more comfortable lives.
The programmers return to Korea for a visit. Ji-pyeong has remained close to Dal-mi and her family and is preparing to express his feelings more clearly when Do-san reappears. Chul-san also reconnects with Sa-ha, who offers to help with his English. Their reunion is interrupted by Dal-mi's urgent call: ransomware has locked Cheongmyeong's files, putting the self-driving project under threat. The company's developers suggest paying, but Dal-mi tries to find someone who can recover the work.
Do-san learns of the attack and calls Dal-mi before rushing to Sandbox. Chul-san and Yong-san join him, and the familiar code helps them find a decryption key. After restoring the files, he sits with Dal-mi and admits that solving the problem felt more exciting than his comfortable job abroad. The three friends decide to stay in Korea. When Do-san returns for the jacket he left behind, Ji-pyeong stops him in the elevator and asks to talk.