It’s no secret that Robin Williams was struggling toward the end of his life. Now, the documentary Robin’s Wish hopes to shine a light on the actor and comedian’s final days. In this exclusive clip, director Shawn Levy opens up for the first time about the changes he saw in Williams on the set of one of his final films.

“I would say a month into the shoot, it was clear to me — it was clear to all of us on that set — that something was going on with Robin,” Levy says of directing Williams in 2014’s Night at the Museum: Secret of the Tomb, the third and final movie in the franchise.

“We saw that Robin was struggling in a way that he hadn’t before to remember lines and to combine the right words with the performance,” he remembers. “When Robin would call me at 10 at night, at two in the morning, at four in the morning, saying, ‘Is it usable? Is any of this usable? Do I suck? What’s going on?,’ I would reassure him. I said, ‘You are still you. I know it. The world knows it. You just need to remember that.'”

Williams died by suicide at age 63, the same year Secret of the Tomb was released. Robin’s Wish, from filmmaker Tylor Norwood and made in collaboration with Williams’ widow, Susan Schneider Williams, will document his fight against the neurogenerative disorder Lewy Body Dementia. Watch the clip above.

“My faith in him never left, but I saw his moral crumbling,” Levy concludes. “I saw a guy who wasn’t himself and that was unforgivable.”
 

Robin’s Wish is available digitally and on demand on Sept. 1.