The woman who stopped one of the most notorious serial killers in U.S. history is speaking out.

Amy Ridgway is the nurse-turned-informant who played a key role in the arrest and conviction of the serial killer nurse Charles Cullen.

Monday on the Katie Couric show, Ridgway discussed the often frightening experience of wearing a wire during meetings with her former friend, Cullen, who killed dozens of patients while working at area hospitals.

Ridgway said she decided to become an informant following an emotional conversation with one of her daughters.

"I explained to her there is a possibility we may not get him," she said. "There is a possibility we could be in danger and we might end up having to move. I was thinking about the worst case scenario and she said, 'Mom.. let's do it."

Cullen is serving life in prison.

He worked at several area hospitals including St. Luke's, Lehigh Valley, Easton and Warren.