The Five Red Herrings (Lord Peter Wimsey #7) by Dorothy L. Sayers

The body was on the pointed rocks alongside the stream. The artist might have fallen from the cliff where he was painting, but there are too many suspicious elements - particularly the medical evidence that proves he'd been dead nearly half a day, though eyewitnesses had seen him alive a scant hour earlier.

And then there are the six prime suspects - all of them artists, all of whom wished him dead. Five are red herrings, but one has created a masterpiece of murder that baffles everyone, including Lord Peter Wimsey.