Pamela Blake, Dennis Moore and Richard Martin

The Mysterious Mr. M is a 13 chapter 1946 Universal Pictures movie serial, the 137th and last serial produced by Universal.

Anthony Waldron intends to steal a new submarine invention from Dr. Kittridge while blaming a fictitious mastermind he calls "Mr. M." To further this plan, Waldron uses a mind control drug he has developed called "Hypnotreme." However, a mystery villain soon appears claiming to be the real Mr. M and starts giving Waldron orders.

Federal agent Grant Farrell, whose brother was killed by Waldron, is dispatched to find the mysterious villain and stop his nefarious plans, teaming up with Kirby Walsh and Shirley Clinton to do so.

Cast:
Richard Martin as Detective Lieutenant Kirby Walsh
Pamela Blake as Shirley Clinton, insurance investigator
Dennis Moore as Agent Grant Farrell
Virginia Brissac as Cornelia Waldron


text from wikipedia