The Atomic Riddle

Available on page 373, <a target="_blank" rel="noopener" href="http://www.isfdb.org/cgi-bin/pl.cgi?GRSBCKYR1999">Bleiler (Gernsback)</a>.

Note: Sam Moskowitz refers to this story as "The Atomic Doom" in his article "The Sleuth in Science Fiction", Jan 1966 Worlds of Tomorrow
Amazing Stories Quarterly, Winter 1928, illustrated by Frank R. Paul.