Leo Gans's international accountancy firm branch's employee Carmen van den Bergh tells at the precinct she beliefs a car deliberately tried to run her down after she noticed serious aberrations in one of shady businessman Lars Hoek's firms' books, but refuses to show the proof. Iris De Graaf, on duty, accompanies Carmen to Harry Breugel's motel, where she's murdered the next night. Screening the accounts and clients, De Cock finds Iris held back crucial information, linking Carmen to a traumatic hold-up with bloodshed 20 years ago, and even a visit that night. He ...
After presumed key-witness Harry Breugel's staged suicide, suspended Iris comes clean about the harp tattoos linking these cases to her bloody burglary trauma and continues her parallel 'investigation', almost leading to loss of evidence. De Cock no longer believes it's about money laundering but links it to accountancy branch chief Leo Gans and his wife's dark past, and not just theirs.
De Cock's sister has died in her retirement home in Urk. During the funeral, De Cock sees "Here lies the seed of Satan" painted on her grave. Back in Amsterdam, a similar text is painted on his house. Meanwhile, Vledder's father is attacked in Vledder's house, and a woman who accused Keizer of sexual abuse, even providing a semen sample, is found dead, leading Keizer to be suspected of the murder. On top of everything, De Cock's wife is assaulted and ends up in the hospital, unconscious.
Following the chain of mysterious attacks, De Cock concludes that a recently released murderer caught by the team in the past is now trying to get revenge. Several old cases are re-investigated. Meanwhile, Keizer is still under suspicion of murder, and Mrs. De Cock finally wakes up.
De Cock and the team investigate the death of a man found on the farmland, and discover that the man was investigating the suspicious recent death of his father. De Cock meets an old acquaintance and is haunted by childhood memories.
Still investigating the murder on Theo Veldhuis, De Cock and his team have uncovered a cattle hormone scandal. Vledder's new flame may be involved in the case, and Vledder doesn't know if he can trust her.
While on holiday with his wife, De Cock runs into an old friend, who appears to have jumped from his balcony the next day. De Cock suspects he was murdered and discovers possible connections to the death of an art expert who claimed that a famous museum piece was a fake. He and his team find themselves in the world of art trade. Vera Prins visits the police station.
De Cock and Vledder escape the explosion at Lowietje's café. Experts say it was caused by a gas leak, but De Cock doesn't believe it. The case seems to be getting over De Cock's head, and, surprisingly, it appears that Prins is involved, too. Den Koninghe reveals that he is quitting soon.