In the Ballroom with the Candlestick — Diana Peterfreund

The dramatic and deadly conclusion to the thrilling YA mystery series inspired by the classic board game CLUE -- now in paperback!
After a tragic accident at Blackbrook Academy kills one of their own, Orchid, Scarlett, Peacock, Mustard, and Plum are desperate to put the pieces back together and finish out the year. The Murder Crew may have earned their nickname, but the last of their secrets are still coming to light and threatening to destroy friendships, futures, and more. And when another suspicious death rocks the campus and Blackbrook's dark past crashes into its present, they have a choice: Band together or turn on each other.
 
Because this year's prom? It's to die for.