Tapestry of Death — Dorothy M. Bowick

The French scientist had found the secret of youth and beauty, and women flocked to his clinic to share it. But beneath that secret was another - of horror and death. Lovely Diana Marshall learns that the unsettling M. Panter's miracles of rejuvenation are more than skin-deep. But do they involve murder? When her coworker disappears, Diana's fears are crystallized. And as Diana and a journalist friend dig deeper into the puzzle, Diana knows that she is next on the ominous Panter's deadly list.