The costume of a plague doctor featured an all-leather ensemble, a beak-like mask stuffed with burning herbs, and a top hat — which signaled that the person was, in fact, a doctor.

In the early 1980s, Griselda Blanco was one of the most feared Colombian drug lords of the Miami underworld.

Fred Rogers, known as Mister Rogers, originally planned to become a Presbyterian minister. But he realized his true calling was teaching children how to love each other — and themselves.

Bobby Fischer had one of the greatest minds the world of chess had ever seen. Only one thing could keep him from holding onto the title of World Champion: himself.

The Kray brothers Ronnie and Reggie may have owned dozens of nightclubs and hobnobbed with celebrities, but they also committed some of the most shocking murders gangland London had ever seen.

Pablo Escobar was vicious, but Don Berna was strategic and calculating — maybe that's why he survived and Escobar didn't.

After the war ended, Klaus Barbie pretended to be a hobo until he was picked up by the CIA to spy in Bolivia and fight against communism.

Before Ringo Starr, the Beatles toured with drummer Pete Best, but differences led to his ousting on the band's very brink of fame.

John Watt's steam engine not only streamlined travel and manufacturing, but was also an impetus for the Industrial Revolution.

He worked for both the Medellin Cartel and the DEA, but eventually, his double life would come crashing down.

For three days in 1934 that Hitler called the "Night of the Long Knives," the chancellor ordered the execution of some 400 Nazis whom he feared threatened his power.