The Fellowship of the Frog by Edgar Wallace

Dick Gordon knew that any discussion with his captors was a waste of breath, and that repartee was profitless. His head was aching, but no sooner was he left alone than he gave himself a treatment which an osteopath had taught him. He put his chin on his breast, and his two open hands behind his neck, the finger-tips pressing hard, then he slowly raised his head (it was an agony to do so), bringing his fingers down over the jugular. Three times repeated, his head was comparatively clear.

The door was of thin wood and could easily be forced, but the room below was filled with men. Presently the light below went out, and the place was in darkness. He guessed that it was because Hagn did not wish the light to be seen from the road; though it was unlikely that there would come any inquiries, he had taken effective steps to deal with the police car which he knew would follow.