The Mysterious Mr. M

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

Plot
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
SOURCE:
 * Richard Martin as Detective Lieutenant Kirby Walsh
 * Pamela Blake as Shirley Clinton, insurance investigator
 * Dennis Moore as Agent Grant Farrell
 * Edmund MacDonald as Anthony Waldron, the original villain
 * Virginia Brissac as Cornelia Waldron
 * Jack Ingram as William Shrag, the chief henchman
 * Danny Morton as Derek Lamont, one of Waldron's henchmen
 * Byron Foulger as Wetherby
 * Jane Randolph as Marina Lamont, one of Waldron's henchmen

Chapter titles
SOURCE:
 * 1) When Clocks Chime Death
 * 2) Danger Downward
 * 3) Flood of Flames
 * 4) The Double Trap
 * 5) Highway Execution
 * 6) Heavier than Water
 * 7) Strange Collision
 * 8) When Friend Kills Friend
 * 9) Parachute Peril
 * 10) The Human Time-bomb
 * 11) The Key to Murder
 * 12) High-line Smash-up
 * 13) The Real Mr. M