Cry Baby by Alex Smith

DCI Robert Kett is about to have the worst day of his life. The city is a Furnace, nine million people losing their minds in an unprecedented heatwave. Somebody is strangling young men on London's buses and trains, and Kett must find the killer before the capital descends into chaos. But that’s not all he has to worry about. An old enemy is out for revenge, and with a price on his head, danger is everywhere. London is burning, but if Kett’s not careful then it’s his life—and the lives of those he loves most—that's about to go up in flames