Blackmail! by Fred M. White — Read

It was a bad day for Stott, the worst day he could remember. For a long time past his nerves had been playing him strange tricks, and now they seemed to have deserted him altogether.

Never before had he been frightened of anything, beyond the horrors conjured up out of his own imagination, but he was afraid now. He no longer trusted his own judgment; he wanted somebody else to rely upon.