In Mayday!Mayday! all players are flight crewmembers aboard flight LK-886, on which the pilot has suddenly died. A heart attack? Poison? Murder? The copilot must now take the lead, but other crewmembers distrust him. The crew believes there are infiltrators amongst them. But who? A skirmish occurs. Will all infiltrators get exposed?

Each crewmember either belongs to the honest crew, or is among the few infiltrators who know one another. At the start you receive 3 identity cards, 2 or 1 honest and 1 or 2 infiltrator. The card you have double, determines your identity. You place these secret cards, mixed, face down in front of you. Then each player looks at 1 card per neighbor. By placing a knowledge tile at a card, you show (or perhaps lie about) what you see. You'll never see more than 1 of another player's 3 cards. So you must combine your own knowledge with the claims of others! But who can you trust?? In order to keep from being unmasked, the infiltrators will naturally act as if they're trying to deduce who might betray the crew.

During skirmishes, some crewmembers will receive first the "Benefit of the Doubt", then they can graduate to a status of "Reliable", and then one of these two reliable crewmembers will become the new Captain. This Captain must start to form a final crew that excludes the infiltrators from access to the cockpit.

With each skirmish, a player sees one identity card held by another player and shares this knowledge (but possibly lies). So each player knows cards self and must value the claims of others. With all players knowing different things, the deductive logic gets deeper and deeper as you theorize about who is who, while also holding possible lies in mind! Will you make it back to the ground safely?