'A fine craftsman' Ellery Queen

When a Swiss professor is found dead on a California university campus only a few feet away from the home of a student he was visiting, Dr Ashwin, a professor of Sanskrit, and Martin Lamb, a graduate student, join forces to find the killer.

The dead man was struck by a blunt instrument but the weapon cannot be found. The only clue is a scrap of paper on which has been drawn an obscure symbol known as the Seven of Cavalry.