The Case of the Amorous Aunt

Perry is hired to help a young woman keep her aunt from remarrying. She makes a good enough case for Paul Drake to get involved.
She also has a fiance, who she is putting through law school. And he turns out to be quite a handful. He gets on Perry's nerves, and then turns into the DA's surprise witness.
But all is not as it seems, and Perry figures it out.

Lorraine Elmore is a well-to-do widow who’s ready to marry again. But nervous Linda Calhoun is certain that the man her aunt Lorraine has fallen for is a fortune-hunting Bluebeard who's out to make a killing--in more ways than one. Perry Mason alloys Linda's paranoia--until Detective Paul Drake digs up enough dirt to convince the lawyer that dashing, mysterious Montrose Dewitt is digging a grave for his bride-to-be.

When the amorous aunt and her amour elope, the chase is on. But when Lorraine's supposedly sinister suitor is the one who ends up murdered, the pressure is on Mason to prove that the blushing bride isn't the one who drew blood.