The unit specializes in the investigation of serial murders and is led by Van der Bijl, a former murder and robbery detective who gained fame for his handling of several high-profile cases. Each episode focuses on a serial killer. The main character, Colonel Piet van der Bijl, also known as Die Byl, is loosely modeled on the famous ex-detective Piet Byleveld.
Byl's team investigates a revenge killing when a drug lord's brother is found with his mouth sewn shut, but coins in his mouth and a teeth-pulling pattern point to a serial killer.
Byl must find the link between two dentists, an undertaker and a home for addicts to stop the Tandem Mouse. They discover another murder scene full of burnt matches.
A murdered chef is found with a number seven written on his neck. Byl suspects number eight is on its way. The team discovers more links between the match victims and the seven deadly sins.
Jo suspects the numbers on the victims' necks indicate a military background. Eliaan orchestrates a shocking confrontation between two men, while Nicki receives bad health news.
The team is involved in a gruesome case when several corpses are found with signs of 'rat bite fever' and human DNA in the wounds. Eliaan targets a journalist as her next victim.
When a critic's body is found, the team must jump in to catch the killer before she can finish her book. Byl and the team make a big breakthrough in the Seven Deadly Sins murders.
A serial killer targets rugby players. Eliaan's motivation becomes more and more clear and Opperman unexpectedly knocks on Byl's door.
The team realizes that the serial killer is deceiving victims through disguises. Lena helps with the Danté murders. Tarina is increasingly in Juan's circle, which puts pressure on his marriage.
Byl realizes that the killer is reaching out to him when she shares personal information with him. Nicki helps locate a possible place for Eliaan to stay, but an armed girl awaits Byl.
The team discovers what really happened when the Slee's house burned down. Byl realizes how sinister Arbortech is. He makes the daring decision to use Aletta Slee as bait.
