The Westing Game by Ellen Raskin and Mac Barnett

A highly inventive mystery begins when sixteen unlikely people gather for the reading of the very stranger will of the very read Samuel W. Westing.

They could become millionaires, depending on how they play a game. All they have to do is find the answer - but the answer to what? The Westing game is tricky and dangerous, but the heirs play on - through blizzards, burglaries, and bombings, Sam Westing may be dead ... but that won't stop him from playing one last game!