Joe Mannix receives an urgent letter from a woman named Lynn Sargent asking him to fly to Arizona. She meets him at the airport and hands him a check for $1,000 and a small sealed package, telling him the money is his fee to take the package to the Los Angeles Police Department. Just as she does so, two men try to take the package, but Mannix manages to retain it after a scuffle. But the mystery deepens when the package turns out to contain nothing but blank sheets of paper -- and the police chief in the town tells Mannix that Lynn Sargent died a month earlier in a hit-and-run accident.