“I was a hobo,” Willy Howard told me. “So was my wife.” It was almost 30 years ago, and I was flat on my back in a hospital bed in Trenton, New Jersey, sharing my room with this elderly man.

The Yellowjackets symbol has appeared multiple times and its meaning and power still terrify the survivors 25 years later. The symbol may have originated from the Hobo Code, with messages such as ...