Crystal Blanchette, the personal chef to Prince, said she saw warning signs. She claims she tried to warn those close to him about changes in the musicians behavior.

In an interview with "20/20", Blanchette said, “There was a change in his moods. Irritable, annoyed, uncomfortable, tired. I felt like I was watching him kind of fade away."

The "20/20" episode, set to air on ABC Friday, will investigate the crisis caused by the proliferation of synthetic opioid fentanyl.

Prince died in April 2016 of an accidental fentanyl overdose.