"I want to warn you that if you put Walter on this you're going to find out what it's all about, one way or the other." Another pause, and I could imagine the face that was peering down at her, a visage to which I was accustomed. "You're sure you want that? Because he's like a gun; once you point him and pull the trigger, it's too late to change your mind."
There's the problem, isn't it? Walt won't stop for anything once he starts. A perennial conflict in the Longmire series is Walt's devotion to his friends/Cady and his duty as a sheriff (often more felt than real), part of its recurrence is because it always works as a plot device (as tired as it may feel -- which is part of the whole thing, it's just as tired for Cady as it is for the reader). Part of that is because I expect that it's a strong reflection of reality (unlike, say the beating that Walt takes in this one and then the near super-human feats he accomplishes shortly thereafter).
Detective Gerald Holman shot himself -- and did so in a fairly unusual manner. That aside, it's a pretty cut-and-dried suicide. But his widow doesn't buy it. Which isn't that unusual, but because she doesn't buy it, their old friend Lucian Connally doesn't buy it -- he's just not that kind of guy. So Lucian drags Walt to the next county and gets him to investigate it -- the sheriff there doesn't see the need, but isn't going to stop him. Lucian gives the widow the warning up above, and she agrees to it, as does Walt -- even with the birth of his grandchild just days away in Philadelphia.
Along the way, Vic and Henry show up -- as does a very unlikely friend of Walt's from a couple of books back. Vic's recovered physically from A Serpent's Tooth, but the rest of her has a bit to go. Henry's just Henry -- and I'm pretty sure that's all he'll ever be. Walt befriends/drafts a local police officer, who also comes through for him in a pretty big way. Actually, meeting Officer Corbin Dougherty was one of my favorite parts of the book:
... he looked vaguely familiar....
"You date my daughter?"
"I did." He blushed up to his blond crew cut. "The first time I came to pick her up you tossed me a shotgun shell."
"Yeah, you said they went a lot faster after eleven o'clock."
I nodded. "I used to think I was a tough guy."
I liked this exchange for a few reasons: 1. It's amusing, 2. It reminds me of one of the best exchanges between Raylan Givens and Wynn Duffy on Justified, 3. It illustrates the difference between Walt and Raylan. I don't know if Raylan will ever get to the point where he could say that last line and mean it, but you know Walt did (and is probably embarrassed that he ever said it in the first place -- Raylan may have rued uttering that to Wynn because of the fallout, but he sure wasn't embarrassed).
The kinds of criminal activity that Walt turns up during his investigation of the suicide and Holman's last cases that probably led him to it makes a guy miss Absaroka County and its apocalyptic cults, generations-long feuds, drug smuggling, serial killers and whatnot. But throughout it all, you know that Walt and his posse will bring justice to those who drove Holman over the edge.
To be honest, the ending of this one felt rushed -- Walt had a hard deadline to meet, and so he had to rush things a bit on his end -- and it felt like Johnson did, too. There was no cheating on the final reveal of his investigation -- Johnson's too careful for that, and he's not one for red herrings, so you know the detail that leads Walt to the conclusion was important when you saw it the second time. But, I didn't think it was well explained, the clues fit, but I didn't see the motive working -- at least not as given. It didn't ruin the experience for me, but it took a little shine off of it.