Upon hearing of several recent robberies of food delivery trucks in Mexico, Joyce Manning (Sally Fraser), Army officer Lt. Col. Glenn Manning's sister, becomes convinced that her brother (Dean Parkin) survived his fall from the Boulder Dam (as seen in The Amazing Colossal Man). [Note 1] Along with Army officer Major Mark Baird (Roger Pace) and scientist Dr. Carmichael (Russ Bender), she goes to Mexico to look for her brother.
Manning had, in fact, survived his fall, but was left disfigured and nearly mindless. Manning is captured, drugged by the Army, taken back to the United States, but again escapes and goes on a rampage through Los Angeles and Hollywood. Eventually, Joyce makes him come to his senses. Realizing what he has done, Manning kills himself by electrocution on high-voltage power lines near the Griffith Observatory.
Who did the Army drug?
Manning