I don't think he was aware of who he was involved with. Whoever he originally contacted sub contracted the murder to the 1+5 group. Once he realised it was too late.
Yes, that actually was the most compelling aspect to the story, to me.
It showed that once you open a certain can o'worms, especially like contracting for someone's death, he had no idea where it might lead.
This show was like a tutorial in the law of unintended consequences.
Even up to and including the possibility that the group might have been wanted to include Marcus as the final target: He, the original contractor, to cover up their own hidden agenda. This might have happened because his own reason for contracting one guy's death was outweighed by theirs--which was to make a social point with their 1+5 killing agenda.
So Marcus went from being the one allegedly in control--who was hiring someone to produce a family inheritance outcome--when he unleashed someone who would have it in their best interests, given the contract was passed on to the 1+5s, to get rid of HIM!
Still thought it wasn't very good compared to other Scandi-crime TV shows I've watched.
The killer and Marcus were both very uninteresting characters, imo. The woman and the detective were quite good though .. and it was nice to see Krister Henriksson again.