In order to find this recipe, you need to get to the second location – the city. There will be a mission where you will be asked to go down the drain for the first time (to pump out the water and get into the City Hall). So, in the sewers there will be large halls with airlocks (where sleeping zombies under water and a spitting fat zombie often live), find the stairs there and always check the room upstairs (after climbing the stairs to the right). There, behind the boxes, you will find 5 neatly folded skulls with an arrow above them near the wall (CEP, as it were, hints what needs to be done). Remember where they lie and go further to the City Hall, as soon as you go to the City Hall, very soon you will come across a staircase, under which a red skull will lie – take it. Then go through the City Hall location and you will be taken back into the sewers. There, soon you will again come across that room with skulls – now you can put the 6th skull on the skulls and there will be a flash – you will receive a secret recipe from the game developers for super weapons. He requires a knife, 5 diamonds and $ 10,000.