Jeff Carter (Lon Chaney, Jr.) is testing a vaccine for influenza. He is working for tycoon, Roger Graham (J. Carrol Naish), who takes the credit and the profit for Jeff's discovery. Roger cares more about profits than safety. Jeff resigns and is blacklisted by his boss.

Jeff heads to South America to perfect the formula. Graham has used this opportunity to release the drug and romance Jeff's attractive wife, Mary (Brenda Joyce). When Jeff hears that his son has died, he takes revenge.