It is a Tuesday evening in the university choir. Lachie Drummond is twenty-two years old, a final-year computer science student, and he sings second tenor with an instinctive sense of line that the conductor acknowledges by directing the rest of the section to listen to him. He is also two moves ahead of everyone in every room he enters. He has been working on a thesis about seams ? the invisible joins in institutional data architecture, the places where different systems meet.

At eleven-thirty that night, he sent a text to a classicist with a choir: a single musical observation, offered as a puzzle, addressed to the person he has decided is the right one to decode it.

By two in the morning he is dead at the base of the Hartley Building stairwell.

Dr Alex Moreton reads the puzzle the way she reads everything: for what it does not say.

The university releases a careful statement about caring for its staff and students and support services.