Child 44 by Tom Rob Smith in Paperback

MGB agent Leo is a loyal follower of the Party, never doubting their orders. He carries out arrests as instructed, even ignoring the brutal death of a young boy. As a devoted soldier of the regime, Leo trusts that his actions serve a greater purpose. However, his beliefs are tested when he is forced to witness the torture of an innocent man and is then tasked with arresting his own wife. Leo knows the Party's motto: trust but verify, especially with those we trust. Now, he must choose between his loyalty to his wife and his own survival, as the killings of innocent children persist.