The Dark Eyes of London by Edgar Wallace

He lifted the telephone, and presently: "Send the first two officers in the building," he said, "and a messenger, quick!" The girl was watching interestedly. Now she saw the real Larry Holt, the man of whom it is said by the Commissioner that "he slept trailing". At his request, she stood outside the open door whilst he conducted an investigation. The light jemmy which the intruder had used he had not troubled to take away. It lay on the floor, and he picked it up with a piece of paper and carried it to the light.

A short thread of cotton adhered to its rough end, which meant that its user had worn cotton gloves to avoid finger-prints. His only hope was the tray. It was a flat glass tray with wicker sides and handles, and he knew that if the gloves came off anywhere it would be here; for a person unaccustomed to working in gloves would remove them to examine the smaller objects. And his surmise was right. When he breathed on the polished back of the gold watch, a distinct thumb-print was visible.