When the game starts, the players will have to find three keys. The keys are somewhere on earth. The only rule of their Endgame is that there are no rules. Whoever finds the keys first wins the game. Endgame: The Calling is about the hunt for the first key. And just as it tells the story of the hunt for a hidden key, written into the book is a puzzle. It invites readers to play their own Endgame and to try to solve the puzzle. Whoever does will open a case filled with gold. Alongside the puzzle will be a revolutionary mobile game built by Google’s Niantic Labs that will allow you to play a real-world version of Endgame where you can join one of the lines and do battle with people around you.