A Secret Gardener?

A man lies dead in the Fellows' Garden at Lichfield College. He's been seen working there, but he's not on the payroll. What motivated him to weed the beds and mow the lawns? And who stabbed him in the back and left him to die?When Geology Fellow Martin Riess happens upon this grisly scene, it is only natural that he should call on his old colleague Bernie and her ex-police friends to help with disentangling this complex puzzle. And it's not long before the official police enquiry is calling on their services too, when this case turns out to have its roots deep in the past.