On this page of our guide to Layers of Fear 2 we have provided a description of third riddle with a padlock which has to be solved during the 4th act of the game. You can get the correct combination by finding the playing cards in the vicinity.
The solution to this puzzle can be solved by reaching the "colorful" room shown in the image, in which, among other things, there is a bloody table with a large number of plates placed on it.
In the same room, you will also find a chest with a padlock.
Look around the area and find the three playing cards lying on the floor - as shown in the image above. They have the correct combination - 676.
You can get to the chest with the padlock and use the correct combination to unlock it. In the chest you will find a miniature tree that emits sound. It will be added to the "collection" in the hero's cabin.