A science fiction mystery short story by American writer Isaac Asimov, which first appeared in the January 1955 issue of The Magazine of Fantasy and Science Fiction and was the first of Asimov's Wendell Urth stories:
Master criminal Louis Peyton spends each August totally isolated on his Colorado ranch behind a powerful force-field. One August, Albert Cornwell takes him to the Moon to retrieve a cache of extremely valuable "singing bells" (lunar rocks which, when struck by the correct stroker, make an incredibly beautiful sound) which Cornwell had obtained by killing their discoverer. Peyton kills Cornwell and hides the bells.
The police contact Wendell Urth to help them prove that Peyton had been on the Moon, so they can psycho-probe him to get sufficient evidence for a conviction. However, since a person can only be psycho-probed once-in-a-lifetime, the police want to be certain that Peyton is guilty.