"You are the country's last line of defense, and I am the only secret within your line of defense."
A national exploration plan codenamed "Deep Blue Door" draws two people with secrets to the intersection of destiny.
Zhou Zhe, codenamed "The Lone Blade", is a sharp blade raised by darkness. He carries a pocket watch that carries the murder and the truth, and seeks redemption in his self-exile.
Shen Zhengyao is a star who is following in his father's footsteps. He is rational and calm but also has a sense of family and country ties and warmth. With his top knowledge and tenacity, he vows to uncover a mystery that has been sealed for twenty years.
Under the extreme environment and the siege of foreign forces, trust is a more luxurious test than survival. When lies and truth intertwine, what they must uncover is not only the mystery of underground resources, but also each other's scarred but still hot hearts.
"Twenty years ago, my father failed to take you home. Twenty years later, I will take you home."
Intention: Deeply trapped in darkness, but still yearning for the light. The salvation of individuals and the protection of family and country are the same song.