In Dead Drop you will find elements of memory games (only with an ever-changing board). There are elements of a spy theme, with the trading of secrets and information and deciding what to keep from your oponents (light, but more than just spy-themed pictures on the cards)... and yes a game this small that actually supports a THEME!
At the beginning of a round a "dead drop" is set up. The dead drop is the information you are after. This card is placed face-down in the middle of the play area and is secret to all players. Next you lay out a number of "stash" cards equal to the number of players. The remaining cards are dealt evenly to the players (for example 2 each in a 4-player game, with 4 cards in the stash area). At this point the deduction begins! Each player has a reference card in front of them displaying how many of each value card there are. The information initially available to you is only the cards in your hand as well as what is in the stash (not enough to determine what the Dead Drop is). Players will have to trade cards with the Stash (1-for-1), trade infomation with opponents (1-for-1), or share information (show an opponent 2 cards and if they have one card equal to the sum, trade one of the shown cards for the sum card). The goal is to not only determine the Dead Drop, but to collect 2 cards whose sum is equal to it (without giving your opponents enough information to do the same).