It's February in the small town of Granville, New Hampshire, and Katie McDonald, math geek and curator of the Avondale Puzzle Museum, is up to her ears in snow and the First Annual Avondale Sudoku Challenge. What began as a small event, geared toward regional Sudoku clubs and individuals, has grown to include competitors from up and down the East Coast.

When the Sudden Death Champion is found 'suddenly' dead, Katie is forced to deal once again with chief of police Brandon Mitchell. He wants to close the fair for the rest of the weekend, but that would be disastrous for the museum. And besides, Katie thinks, all the suspects are already in one place.... How hard can this be to solve?