"Does anyone else in the house keep gas going all night?" he asked.
"I don't know," was the reply. "Most of them, I know, use electricity."
"Nobody else has been overcome as he has been?"
"No. Plumbers have minutely examined the lighting system all over the house and found nothing wrong."
"Does the gas in the house all come through the same meter?"
"Yes, so the manager told me. This meter, a big one, is just off the engine room. I supposed it possible that some one shut it off there on these nights long enough to extinguish the lights all over the house, then turned it on again. That is, presuming that it was done purposely. Do you think it was an attempt to kill Henley?"
"It might be," was the reply. "Find out for me just who in the house uses gas; also if anyone else leaves a light burning all night; also what opportunity anyone would have to get at the meter, and then something about Henley's love affair with Miss Lipscomb. Is there anyone else? If so, who? Where does he live? When you find out these things come back here."
* * * * *
That afternoon at one o'clock Hatch returned to the apartments of The Thinking Machine, with excitement plainly apparent on his face.
"Well?" asked the scientist.