The Lonely Bride by Fred M. White

A thrill passed through the spectators, there was a murmur, followed by profound silence, as Carden held the bottle up to the light. It was only a tiny phial, no larger than a bottle of marking-ink, but everybody felt that it might hold the fate of some desperate criminal. The tiny blue object was handed up to the coroner, and he examined it through his glasses gravely.

-"I should like to know where this came from," he said. "Will you be good enough to tell the court where you found it?"