Showing Crucifixion Creek: The Belltree Trilogy (Book One) by Barry Maitland

Homicide detective Harry Belltree wouldn't usually be looking too hard at an elderly couple's suicide pact. Especially now, when his brother-in-law Greg has just been stabbed to death. But it seems Greg and the old couple had ties to the same man, a bent moneylender with friends in high places - and low. Harry can't get officially involved in Greg's murder, but he suspects a link with two other mysterious deaths: his parents'. And when he goes off-grid to investigate, that's when things start to get dangerous.