Marine biologist Su Lan has spent her life pursuing the legendary "Heart of the Deep Sea" - a mysterious coral that emits unique sound waves and soothes all living creatures. Three years ago, during a scientific expedition to the "Devil's Eye" area of the South China Sea, her fiancé, top diver Lu Qisheng, died in the deep sea trying to save her, leaving a wound that she could not heal. From then on, Su Lan closed her heart and poured all her emotions into the cold research data.
Three years later, a mysterious investor named Shen tide landed at the research institute. He brought huge amounts of money and the most advanced equipment. The only condition was that he join the scientific expedition team in person and return to the "Eye of the Devil" with Su Lan. The appearance of Shen tide was like a huge stone thrown into Su Lan's dead heart. He has diving skills that are strikingly similar to Lu Qisheng's, is familiar with every detail of her habits, and can even accurately predict her fears in storms.
When the dusty memories are pried open again and again, and when the dangerous deep sea stirs up waves again, Su Lan is forced to face a cruel truth: Is the Shen Xi in front of her an old love who has returned with a secret, or a stranger with careful planning? Under the unpredictable deep blue, she not only wants to find the legendary miracle, but also to find the heart lost in the tide.
