"I am now going to switch on the ultra-violet light. If the filter is perfect, you will not be able to see the light, because ultra-violet rays, when unadulterated by other rays, cannot be seen by the human eye. There. The light is on. "I have offered evidence to Sergeant McGinty in which I intended to prove that Biggert, William Weedham's secretary, was killed because he was about to show to William Weedham a check to which William Weedham's signature had been forged. Not only that, but the forger, in cashing the check, also forged the endorsement of Major Paxton, to whom the check was made out. "I have further pointed out to McGinty, that this same killer disposed of Jack Carlson, after Carlson had been betrayed by a woman. This woman must have been Carlson's friend. She must have known all his secrets, including the fact that Carlson was the Eye. She gave all this information to another man--the same man who forged the check which I mentioned before. Then she assisted this killer to shoot Carlson. This woman's face powder was treated with naphthionate of sodium. A little of this powder rubbed from her cheek to Carlson's lapel made Carlson a perfect target in pitch darkness, provided that darkness was penetrated by rays of invisible ultra-violet or black light. I have a sample of that woman's face powder here on McGinty's desk." Black Hood turned the ultra-violet lamp on the desk. The box of powder there became phosphorescent. "When I was framed for the Tauber jewel robbery tonight, I seized the opportunity to toss some of this face powder onto the jewels in the robbers' bag," Black Hood continued. "The face powder is that of Vida Gervais. Watch, please." Black Hood turned the ultra-violet lamp out toward his audience. Vida Gervais' frightened face glowed in the black light. Startled gasps could be heard from the others in the room as they stared at that ghostly face. "Vida Gervais," Black Hood continued, "knew a good thing when she saw it. To eventually better her social and financial position, she was willing to sell out Carlson, alias the Eye, to another man who, if he could accumulate, through fair means or foul, quite a tidy sum of money now would get his hands on a great deal more money in the future. "So Vida Gervais betrayed Carlson, alias the Eye, into the hands of the man who had killed Biggert. The forty thousand dollars which this man had got from the forged check was a small part of the money he needed. But if he could step into the Eye's shoes for a little while, he could rapidly accumulate the rest.