Gunman's Bluff by Edgar Wallace

Margaret Maddison had spent a torturing two hours before the shabby messenger had brought her the note which told her at least that Luke was alive. At the bottom of the letter there was scrawled in a different hand -- Connor's own -- "Come round about eight. " The postscript he had not communicated to the Gunner.

The letter confirmed all she had feared. She sat motionless at her desk for half an hour with the copper-plate communication before her, trying to formulate a working theory. Luke was in trouble -- had trouble. She had accepted this fact as a starting point. In her mind she did not reproach him for the monstrous eccentricity which had brought him to his present position -- rather she hated herself that in a moment of crisis she had deserted him and urged him into deeper folly.