...of a spy

He walked rapidly away. He didn't bother to see whether he was being followed, to check up on the shadow. But, passing by the end of a street, he happened to turn, and there just around the corner, pressed against a wall to escape notice, was a thick stocky figure. Martins stopped and stared. There was something familiar about that figure. Perhaps, he thought, I have grown unconsciously used to him during these last twenty-four hours; perhaps he is one of those who have so assiduously checked my movements. Martins stood there, twenty yards away, staring at the silent motionless figure in the dark street who stared back at him. A police spy, perhaps, or an agent of those other men, those men who had corrupted Harry first and then killed him - even possibly the third man?

[The Third Man, Greene, G.]