It is a quiet and lonely night at the beach. The gentle splashing of seawater creates a sense of serenity. From afar, the sound of a motor being started can be heard. On board a speed boat, the back of a man is seen trying to start the engine, but it splutters and refuses to start. The man turns around to face a huge black plastic bag. The bag seems to contain a motionless body. Thereafter, the man gets off the speed boat and walks on the beach. He is getting some tools to fix the engine. A while later, the black bag moves. Suddenly, it is slashed from inside to reveal the sharp edge of a shard. The bag is slashed open and a girl emerges from it, gasping for breath and looking terrified… The girl undergoes a medical examination that confirms she has suffered sexual and physical abuse. Assistant Superintendent Zhou Jianfeng (Desmond Tan) comes on the scene and meets Qiu Xueqing (Rui En), a psychiatrist. Using hypnosis, Xueqing leads the girl to relive her experience that elicits an important clue. The perpetrator is suspected to be Di Shen (Christopher Lee), a suspense novelist. Jianfeng uncovers clues that implicate Di Shen in the case. Di Shen also realises that the suspect has enacted the plot of his novel which raises the possibility that he is a fan of his work. To prove his innocence and satisfy his own curiosity, Di Shen gets involved in the case to identify the suspect. The girl is silenced by the suspect. Xueqing is the only person who have seen him. She reproaches herself for not doing enough to protect the victim. While working together with Di Shen in the case, she is kidnapped and imprisoned. At the brink of death, an idea came to Di Shen who eventually saved the dying Xueqing. Xueqing becomes paranoid after recovering from her ordeal. Her insistence on making sure that all doors are locked before and after leaving the house is a clear sign that she has developed obsessive compulsive disorder and claustrophobia. Di Shen does all he can to help Xueqing face her inner fear and overcome it. Xueqing, on the other hand, feels secure in Di Shen’s presence. Their relationship warms up. With help from Di Shen and Jianfeng, Xueqing finally overcomes her fear. The suspect’s identity is exposed, but he disappears with the police in hot pursuit. Shortly after, Jianfeng, upon receiving a tip-off, found the suspect being locked up in his own car's boot. The suspect admits that he had imprisoned and killed six women, but when questioned about why he ended up in his car's boot, the suspect claims that he was held captive by a mysterious man who subjected him to the same torture that he had inflicted on his female victims, and forced him to confess to the murders. Jianfeng suspects that someone is secretly sentencing the suspect. Who can it be? A series of crimes occurred in the fashion of Di Shen’s plots in his novels, as if real-life events are being portrayed on screen. This mysterious man is using unlawful means to mete out justice on suspects who have escaped punishment and forcing them to confess to their crimes. It is obvious that he is sending out a warning message to lawbreakers. All this reminds Di Shen of what happened seven years ago… Seven years ago, Di Shen was a University employee who befriended a group of students when he was studying psychology in private. Their failure to find a goal in life caused them to feel lost. Everyone wanted to find a niche for themselves to prove their worth. This group of friends happened to do a good deed one day and became heroes. The immense joy they felt dawned on them that their mission in life was to uphold justice! Di Shen and his companions carried out secret missions to uphold justice and even resorted to unlawful means to achieve their goals. They considered themselves dark crusaders of justice, and imagined themselves to be Robin Hood and his merry men. Then, a university professor murdered a female student but got away scot-free. While trying to force a confession out of the professor, Di Shen and his teammates accidentally caused his death. Everyone felt that the female victim’s death was avenged when the professor died, however, Di Shen began to wonder if his sense of justice and taking the law into his own hands was morally right. Then, the death of a team member reinforced his belief that what they were doing was wrong. He disbanded the group, left the university and subsequently lost touch with his teammates. After reflecting on his behaviour, Di Shen gives up his extremist views. Instead, he hopes to reform criminals through psychological methods, but now, a self-professed upholder of justice calling himself “Shadow Walker” has surfaced to punish criminals in the quiet. Di Shen becomes the prime suspect. Also, the fact that he believes humans are evil by nature and therefore, they need to be re-educated to curb their criminal tendencies points to Di Shen as the “Shadow Walker”. Shadow Walker punished the criminals in his own ways. Di Shen tries his best to prove that he is innocent, but in the end makes Jianfeng and Xueqing more suspicious of him. Is Di Shen really Shadow Walker? Relying on her special ability to feel like the criminal, Xueqing begins to take an interest in the efforts to track down “Shadow Walker”. Di Shen also joins in to prove his innocence, but as the investigations deepen, more and more suspects surface. The suspense escalates. They begin to realise that every suspect harbours a secret. Perhaps deep down, everyone wants to be the Dark Knight to uphold justice. “Shadow Walker” may be more than one person. Ever since she was a child, Xueqing has the innate ability to feel someone’s mood, so she makes use of hypnosis to enter her patients’ subconsciousness. She can also penetrate the criminal’s psyche at the crime scene to reconstruct his criminal trail. Her special ability helps to reduce the time it takes for Di Shen and Jianfeng to deduce the developments of the case and discover new clues. As the investigations progress, feelings developed between Xueqing and Di Shen and they become a couple. Jianfeng, who hides his love for Xueqing, is heartbroken, but what irks him is that Xueqing continues to trust Di Shen despite all the evidence pointing to his guilt. Jianfeng does not want Xueqing to be deceived, so he is determined to unearth evidence of Di Shen’s guilt and to show his true colours to Xueqing. Xueqing gradually notices Di Shen’s abnormal behaviour. She has a nagging feeling that he is linked to “Shadow Walker”. Probed by Xueqing, he finally discloses his secret… Their relationship goes into a crisis. Xueqing’s distress resulting from suffering several blows makes her unable to differentiate between good and bad anymore. Every time Xueqing slips into the murderer’s psyche at the crime scene, she is consumed by the character and ends up disoriented… Di Shen harbours the bitterness that his mother was brutally murdered. As he moves closer to the truth, he discovers that it is not what he has imagined. His long-held belief crumbles, and he is crushed. Will Di Shen walk out of his gloom eventually and get back to his feet? Will Xueqing get carried away and turn villainous against Di Shen? Will Jianfeng suppress his obsession to nail Di Shen? What will their love and conflicts lead to? The three of them are inevitably drawn into the cases. As they close in on the truth, it appears that they are also moving closer to their inner secrets. Against The Tide will let you walk and experience the feelings of the different characters.