In the deck, there are 5 cards for the psycho killer and cards for the weapons he uses to attack you.
Your turn consists of playing as many cards as you like from your hand but must end by you drawing a card from the top of the deck. However, you do not need to play a card to draw from the deck.
If someone draws a Psycho Killer card they must play it on the table in front of them, unless they can evade the Psycho Killer. If they cannot, every player with a weapon card in their hand gets attacked.