Na Kyung-soo, a diver, is angered to learn that the Coast Guard is assigning responsibility for the death of a fellow diver during the Sewol ferry disaster recovery to Ryu Chang-dae, the representative of civilian divers, and charging him with manslaughter.

After a high-ranking North Korean official requests asylum, KCIA Foreign Unit chief Park Pyong-ho and Domestic Unit chief Kim Jung-do are tasked with uncovering a North Korean spy, known as Donglim, who is deeply embedded within their agency. When the spy begins leaking top secret intel that could jeopardize national security, the two units are each assigned to investigate each other.

Kyung-hak, who has been studying to become a police officer, is forced to pay back his mother’s debt of $20,000. Already struggling and having to work part- time while studying, Kyung-hak is now forced to make big monthly loan payments on top. Eventually, Kyung-hak stops studying and becomes a deliveryman to make ends meet. Meanwhile, cracks start to form in his relationship with his beloved girlfriend Hye-jin.

Hae-woong, an assembly member candidate, is taken out of the running because he became a thorn in the side of a local bigwig, Sun-tae. Hounded by loan sharks, due to defaulting a campaign loan, he decides to get his hands dirty. He steals classified government’s information about an urban development plan and obtains the help of a local gang leader, Pil-do, by promising hefty real estate profit. Now Hae-woong re-enters the race and tries to take revenge on Sun-tae. Unbeknownst to him, his messy journey through politics has only just begun.

The city hums with its usual noise and haste. Unable to keep pace with its restless speed, Se-yeon moves slowly, as if walking through a different time. Every day she brews her tea carefully, hangs her laundry, heads to work, and eats alone. She has a dream, yet never steps into it - only circles around it. Avoiding people's eyes, she goes to the darkened river after sunset and paints. It is the only moment she feels she is reaching toward her dream, the only moment she feels alive. There, in that night river, is someone else besides Se-yeon. By the same river, Jae-woo dreams as well - a dream of making a fortune by selling river sand. They share the same river, share meals, walk the same path, and spend a season together. At the end of summer, Se-yeon and Jae-woo finally come face to face with each other's fragile truths.