However, to me this book was more of a group book; there are several intertwining plotlines, mostly with couples in various stages of their relationships, and most of them seemed just as important as Vinh and Hannah's romance. The ongoing saga of Decker, Sophia, and Dave reaches a crisis point when the Troubleshooters commander brings in a therapist to deal with everyone's trauma, and it looks like this plot will become a focus in the next book; over in the land of Navy SEALS, Izzy Zanella falls in love at first sight and ends up marrying a pregnant teenager (age 18) even though he's not the father of her baby; I suspect their plot will continue later in the series, as well.
As is usual with Brockmann, there's also a complex suspense plot involving the murder of Tim Ebersole, leader of a cult of white supremacists who was involved in Angelina's death. The cliffhangers at the end of the scenes are really well done. This was a great book to have while traveling as it was difficult for me to put down.
Brockmann continues to include characters of various races. Lindsey Fontaine Jenkins from Into the Storm is back as a supporting character, Jay "J-Lo" Lopez has some good scenes, and Vinh Murphy is half-black, half-Vietnamese, which has some effect on plot events. I do wish Brockmann would run a search on the word exotic in reference to eyes before she finishes her manuscripts, though!
I think there's enough information provided that one doesn't have to be familiar with the series to understand what's going on. Your mileage may vary. I think it would be a big help to read Flashpoint, which I believe is the book whose events are most relevant to this one.