The Things is a game for five or more players, and simulates the paranoid members of an antarctic research facility being overrun by - or conquering - an invasive shapeshifting alien.
This game was never fully playtested. Card trading probably needs to be loosened into a Settlers-of-Catan style haggling. ("I want a 5, I'm willing to trade a 2 or a 3 for it.") I ended up making a street game version instead, and never came back to this.
Remove the jokers from the deck.
Starting at the bottom of the deck, count out the first X black cards into a new pile, where X is one less than five times the number of players (so for three players; fourteen). Add the queen of hearts to this pile.
Shuffle this pile, and deal a hand of five cards from it, to each player.
Shuffle the rest of the deck, and place this deck face-down in the middle of the table.
There are two card piles - the draw pile and the discard pile. When players draw cards, they take them from the draw pile - when they discard them, they place them face down on the discard pile. If the draw pile runs out, shuffle the discard pile to form a new one.
Club and Spade number cards are human attack cards - their numerical value represents their effectiveness in combat.
Club and Spade face cards represent Flamethrower attacks.
Heart and Diamond number cards are Thing attack cards - again, their numerical value is their combat rating.
Heart and Diamond face cards represent Bite attacks.
If a player's hand consists solely of Clubs and Spades, they are Human.
If a player's hand contains any Hearts or Diamonds, even just one, then they have become a Thing.
A random player is chosen to start, and turns progress in alphabetic or clockwise order.
On each of their turns, a player may choose either to Search, Converse, perform a Blood Test or Attack.
If a player chooses to Search the camp, they draw a single card from the draw pile and look at it. If it is a Heart or Diamond and the player is not a Thing, they must discard it. Otherwise, they can either discard it immediately, or add it to their hand and discard a card.
If a player Converses, he or she should pick a card from his hand and call out its number, and say what card they'd like in return for it. Each other player may then offer a card to trade for it, by calling out that card's number. The caller must accept one of these trades, and swaps cards with the trader. (The trade must be honest, so far as numbers go - anyone unable to honour a trade must leave the game.)
If nobody responds to a call for Conversation, the caller may choose a player; that player sets aside one of their cards (if the victim is a Thing, it must set a red card aside), and has the caller take a card at random from those which are left. The caller then gives them the card that was being offered.
If a Thing only has one Heart or Diamond in its hand, it may not trade it away (as this would revoke its Thingness). It may trade its other red cards, however - indeed, this is the only way in which a Thing can infect other players.
To perform a Blood Test, a player must show a Flamethrower card to all players, and discard it. They may then nominate an opponent, who must reveal a randomly-selected card from their hand.
To Attack, a player nominates their target and plays any number of attack cards (Human or Thing) face up from their hand. Any other players may join the attack by playing further attack cards. In response, the attacked player may play a number of attack cards in his defence, and this may be boosted by other players. Attackers may play further cards to increase their attack again, defenders may then boost their defence further, and so on until nobody wants to play any more cards.
If a player plays a pair of cards of the same number, at the same time during an attack, that pair counts as if three of such cards were played. (If Aleric plays the 6 of Spades and the 6 of Clubs, it counts for 18 damage, rather than 12.) If a Thing is able to play three cards of the same number, they count as four; four count as five. No bonus is given for multiple face cards.
(A Thing may never play its last Heart or Diamond as part of an attack, as this would revoke its Thingness.)
If the cards played in attack total more than the cards played in defence then the Attack is successful and the victim is killed; otherwise it fails, with no effect.
If any Flamethrower or Bite cards were used, however, the success of the attack is determined purely by the most of such cards on a given side - all numbered cards are ignored. In addition, failing an attack against a defender using a Flamethrower or a Bite will kill the player who initiated the attack. (A single player cannot Bite and use a Flamethrower in the same combat.)
When a player is killed, their hand is dropped face down onto the discard pile - they take no further part in the game, and are not allowed to reveal whether they were Human or Thing until the endgame.
At the end of each turn, any player who now has less than five cards in their hand should draw back up to five. If a Human draws a red card, they must show it to everyone and discard it face-down, and draw again. If a Thing draws a red card, it may choose to keep it or (pretending to be human) openly discard it and draw again.
A Human player may, at any time, decide that the camp has been cleansed and that it's safe to radio for a rescue plane. That player reveals their hand, and declares that the game is over.
All other players then reveal their hands. If any Things are shown to be still alive, then they are unleashed upon civilisation and win the game. If only Humans remain, however, then the Thing has been vanquished and the Humans win the game.
A Thing player may, at any time, decide that the camp has been cleansed and that it's safe to build a two-seater flying saucer and head for civilisation. That player reveals their hand, and declares that the game is over.
All other players then reveal their hands. If any Humans are shown to be still alive, then they manage to sabotage the saucer and destroy the Things in the process. If only Things remain, however, then they merge into a single two-seater blob and fly off to conquer the world.
The only way in which a player can become a Thing is to be tricked by an existing Thing during Conversation; it follows that every Thing must therefore have a 'parent', and that any Thing who cannot cite a parent has drawn one or more red cards illegally.
Conversely, any Human who was definitely infected by a Thing can only have gotten rid of their red card illegally.
If a player realises they are Human despite having been infected earlier, or are a Thing without ever having been infected, then they must discard their hand and leave the game, succumbing to death by exposure.
If a mistake is only revealed during endgame ("But I am a human! I destroy your saucer!" "No you don't, I infected you ages ago."), then work out what each player really is, and use that to see who wins.
The Things was invented before I'd read about Cpl Ferro's Thing card game. I'd have called it a day and accepted the hand of convergent evolution, if Cpl Ferro's game had covered the paranoid who-infected-who business as well, which was the main thing I was trying to capture here.
Due credit to Eric Nussberger for the card-pair trade-incentive suggestion. A few years later someone suggested some rule changes on BoardGameGeek.