You thought you had the trail well covered.
That note was written not by Miss Donovan, but by the blonde in your outfit.

The whole trouble is that your abduction of Stella Donovan was witnessed from a back window of the hotel." Lacy leaped to his feet, but Westcott's gun rose steadily, and the man stood with clenched hands, helpless in his tracks.
"Who says that ?" he demanded.
"I am mentioning no names at present, but the very fact that I know these things ought to be sufficient.

You better sit down, Lacy, before you forget yourself and get hurt.

If you imagine this gun isn't loaded, a single step forward will test it.

Sit down! I am not through yet." There was a quiet, earnest threat in the voice which Lacy understood, the sort of threat which meant strict attention to business, and he relaxed into his chair.
"I'll get you for this, Westcott," he muttered savagely, hate burning in his eyes.