

A sitcom about a group of students who have a phobia of English. They are enrolled in a "Secret Class" that is known for a high success rate of teaching students English. Each student has their own 'secrets' and problems with studying English.

In August 1950, waiting for UN troops to arrive, the South Korean army assembled to protect Nakdong River. Only 71 student-soldiers are left behind to guard the city of Pohang. Now they are on a mission to defend the country from North Korean troops.

During fourth period, high schooler Da-jeong finds her classmate Tae-gyu dead in a classroom and Jeong-hun standing in front of him with blood on his clothes. In order to stop Jeong-hun from becoming the prime suspect, Da-jeong must help him find the real murderer, who is still inside the school building, under 40 minutes before period four ends.

Jang Baek-Ho is released from prison after 4 years of incarceration. He wants to open up a noodle restaurant, but he discovers that 5,000 dollars is missing from his bank account. Jang Baek-Ho then tries to find his wife and 3 children. Their secret is revealed.