Muddy Waters by Candace J. Carter

Henry "Whispering" Smith is a range detective for the Colorado Plateau Cattlemen's Association.  He picks up rustlers who try to steal cattle.  He's good at his job.  Buy when he gets a call that his father has cancer, he decides to go home for a while.  He and his father parted in a fight and he's not eager to see him but he doesn't want to have regrets later.

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When he arrives in town he finds an old friend there.  He'd picked him up for rustling in the past but Aubrey saved his life when his partner in crime tried to kill Smith.  Neither one holds a grudge and they enjoy visiting again.

Aubrey asks him to go on a ride with him and takes him to a long forgotten pasture land.  He shows him the cows in the pasture and indicates that two are missing.  He states he's not rustling anymore and that he suspects it's the family from the slaughter house he works at that is thinning the herd.  He's afraid he will be blamed for it because of his past.  Henry agrees to look into it.

When he goes back to the pasture, he finds Aubrey, dead.  Was it the slaughter house boys, someone trying to find the lost treasure that's rumored to be on the farm, or someone else who is the killer?

When Henry is searching for answers, someone is setting him for murder.  The youngest of the slaughter house boys is found dead and the killer used Henry's pistol to kill him.  He can't remember when he saw it last,  It was in his truck and now he has become a suspect.

When he figures who the killer must have been, it gets deadly.  With more than one person gunning for him, will he get out alive?