Riddle's calculation

Tom Riddle is invited to the Malfoys' Christmas Ball. One of the other guests is Dumbledore. Dumbledore cannot take his eyes off him, his gaze follows Tom at every turn. When a murder occurs and Tom's plans for the future are jeopardised, he is forced to uncover the perpetrator. To do so, he must work with Dumbledore. His calculation is risky, nevertheless. [50's/Crime/Oneshot]