Contains spoilers for this episode and earlier episodes.
Dal-mi needs one more member to complete Samsan Tech's hackathon team and persuades Sa-ha to join as its designer. Chul-san and Yong-san worry about their new chief executive's lack of a university degree, but Do-san asks them to trust her. With In-jae recruiting experienced developers, the sisters begin the competition from very different positions. Dal-mi must turn a group still questioning her credentials into a team capable of presenting a business together.
Using handwriting data, Samsan Tech develops a service to distinguish genuine signatures from forgeries. Its first approach struggles, and Do-san rebuilds the network under pressure. The revised system achieves a strong result before the presentations. Ji-pyeong offers a personal investment if the team fails to enter Sandbox, then helps Dal-mi prepare her pitch. Outside the competition, he hears about the sacrifices Won-deok and Dal-mi made after Cheong-myeong's death and regrets not helping them sooner.
Dal-mi delivers her presentation successfully, earning her colleagues' confidence. In-jae then demonstrates a system that creates new fonts from handwriting. Chairman Won asks whether Samsan Tech can detect the competing system's output as a forgery, and their live demonstration fails. Do-san takes the setback personally, while Sa-ha doubts the team can advance. Before Ji-pyeong can answer Dal-mi's questions about his earlier deception, Do-san arrives with the selection result: Samsan Tech has been admitted to Sandbox.