he genius of Robin Williams is taken as a given by this intensely sad documentary, which pays fleeting tribute to the actor and comedian’s talent but focuses mainly on the undiagnosed neurodegenerative disease that led him to take his own life in 2014. Lewy body dementia is a deadly and devastating condition, one that is little known and frequently misdiagnosed. And for someone like Williams, whose brilliance depended on the quickfire, sparking neural connections of his exceptional brain, the symptoms, which include fear, delusions and hallucinations, must have been particularly terrifying. This film, made at the behest of Williams’s widow, Susan Schneider, is intended to raise awareness of the condition. It’s certainly informative and affecting, but the limited use of early archive footage and the emphasis on Williams’s decline and suffering make for bleak viewing. • On multiple VOD platforms