His presence on set has been “essential,” the “Indiana Jones” actor told Variety in an interview published Wednesday, saying that Fox “gives me both a physical representation of the disease to inform myself with, but more than that, he allows me to believe that Paul could believe that he could be adequate to the challenge.”

It’s been essential. Michael’s courage, his fortitude and his grace, more than anything else, is on full display. He’s very smart, very brave, noble, generous, passionate guy, and an example to all of us, whether we’re facing Parkinson’s or not. You cannot help but recognize how amazing it is to have such grace.

Fox came out of retirement to star in the series, which features Ford as a therapist who has Parkinson's disease