Not direct evidence that Collins was guilty, but circumstantial evidence of the highest importance.

Not only had he threatened to kill the merchant, but he had motive for the crime, and a motive which could be established easily in a court of law.
"You say Collins will be at your house at eleven to-night ?" inquired Britz.
"Yes," she answered, an eager light in her eyes.

"And if you care to be there and will listen, you shall hear him confess the crime." Her words and the tone of certainty in which she spoke almost dazed Greig.

Even Britz had to struggle hard against betraying his amazement.
The whole thing seemed incredible--yet the detectives had experienced more incredible happenings in the course of their long service.
"You say he will confess ?" Britz said mechanically.
"More than confess," she answered.

"You'll hear him gloat over the crime.