Could it be that A Gun for Sale is the turning point in Greene's canon that I've been looking for? The point when he departs from the formulaic thriller and adds a dose of irony and contemplation?
"Mather wanted to say: Listen to me. Your damned jumble is of no importance. My girl’s in danger. She may be dead. He wanted to do things to people, but he stood there heavy, immobile, patient, even his private passion and fear subdued by his training. One didn’t give way to anger , one plodded on calmly, adding fact to fact; if one’s girl was killed, one had the satisfaction of knowing one had done one’s best according to the standards of the best police force in the world. He wondered bitterly, as he watched the vicar search for his prayer book, whether that would be any comfort."