The Playing Cards- What Do They Mean?

I've already stated that the playing cards on the clue board represent the family and the suspects, however we decided to add more to the story so the cards make more seance and so that they have a purpose. We have decided to add the fact that the main antagonist and protagonist were former best friends and used to play a card game called 'killer'. After the kidnapping occurs, Ace is left with a pack of cards and a note. The cards helps Ace know who he is looking for and Ace has to play the game again...in real life.