This was a great book, yet another great one by RFC and JacobHolo. Thanks for the addition to the series. This was another detective mystery, though this time it didn't start with murder. Our intrepid trio (because you have to count Cephalie) and Specialist Nina Cho are on their way to a well-deserved vacation when a prank threatens to derail the goodwill between the two universes. What follows is a well-detailed detective story, mostly focused on Detective Isaac Cho but with some good moments of character building for Agent Susan Cantrell. They follow leads and get frustrated when that doesn't pan out, which I assume is why we need detectives in the first place, because if it were easy, anyone could do it. This plot is intricate and keeps the reader at the edge of their seat until near the end. I recommend a good lounging chair.
This is the Gordian Universe, so time travel does feature into it, as it has to, but it's means to an end. It's used where it's possible to use, and not overused. One might ask if they couldn't have used earlier, as in the prank and the second incident, but on closer inspection it's obvious they wouldn't have learnt anything. All the people involved and all the pieces were in evidence, so time travel wouldn't have revealed anything they didn't already know. (And unnecessary time travel is still not allowed in the SysGov universe, since the The Valkyrie Protocol's conclusion)
I couldn't guess who really was the culprit. Oh, I had my suspicions, because of actions said character undertook, but like Cho and Cantrell, we weren't given enough information to form a complete picture. The plot necessarily had to be more complex to explain what was going on. And knowing the authors, I know they wouldn't go beyond throwing a distraction or two, which could be later explained away (and they did).
The book ends with "what are the chances of this being needed again?" Well, given that The Dyson File is on the horizon for November, we know they are pretty good.
I'm also wondering when the minor B plot that the Big Wigs are involved in will show up. I think Jacob posted here he was in an universe-destroying diet for a couple of books, so maybe Book 6? I want Raibert Kaminski again, and Kleio!
Finally:
"Evil resides in every heart [...] We all struggle with it, and most of us triumph more often than we don't. It's a private war in every person, but we don't wage it alone."
- SysPol Detective Isaac Cho