Bloodlands by Mark Dawson is Book 23 in A John Milton Novel Series.
John Milton is no stranger to betrayals. He's been experiencing them from the moment he left Group Fifteen. And ever since then, he's been on the move and going dark. His IT specialist Ziggy (and former MI6) has done the hacking necessities and information gathering for John, and John has rescued him from a scrape or two. Although they're two completely opposite personalities - Ziggy being a total geek and John the former Number One of Group Fifteen master operative - they need each other in different capacities. Ziggy wants to be of help, and he can do it all technically, providing, or knowing who can, all the necessary things for traveling and existing without a leaving a trail.
John and Ziggy are on the run when the story opens, trying to determine the whereabouts of Control of Group Fifteen since she and the group of agents with her including John were sabotaged by one of their own in Russia. She, the saboteur Lily Moon, Number Six, promises her defection while Control is captured, and Milton manages to get away in the mayhem after all the agents are executed. The defector returns to the Group with a story about her miraculous escape while having promised the Russian she'd supply critical information to spare her young daughter (Lola) and earn the money necessary to fight to retain custody of her.
John knows her story implicated him in the murders of Control and the agents and knows the pursuit is in full operation to capture or kill on contact. Ziggy and John are in it together as their escape leads them to France first, Ukraine second. John tries to persuade Ziggy to let him go the rest of the way alone to find Control and rescue her from her captor if she's still alive, but Ziggy is unwilling to give up.
Another former acquaintance of John gets involved and the action accelerates in all kinds of ways in an effort to get the information they need to find Control.
Bloodlands is a bleak tale of systematic necessities of violence and captures, excessive and extreme travels, seemingly unending miles over desolate terrain, and the pursuit of mixed objectives. Each character demonstrates full allegiance to the search with deadly intentions and the somber knowledge of their possible deaths before accomplishing their goals. All done to rectify horrific wrongs and clear John's and eventually Ziggy's and his other friend's names. It's a horrid journey with slim rewards along the way but the gut-level do or die determination is the one shared absolute.
The conclusion is stunning although there are hints of its existence before the ending so the surprise is somewhat expected but not pleasant while setting the stage for Book 24.
I highly recommend A John Milton Novel Series, and even though 23 books are a lot to read, doing so really will add the complete picture of the characters, especially Milton, if you start at the first one in the series.
(Some profanity.)
Father, only you know people's hearts. I pray each one who's using the talents you've given them would know it was you who gave them what they love to do. In the Name of Jesus, Amen.