From PBS.org:

Returning to television for the first time in nearly three decades, two-time Academy Award®–winner Glenda Jackson stars as a woman desperately trying to solve two mysteries as she declines ever deeper into dementia, in Elizabeth Is Missing, an adaptation of Emma Healey’s acclaimed novel.

From PBS Passport currently you can stream this 1 hour 27 minute film.  Amazon Prime requires that you pay to stream.

Again from PBS.org:

Jackson astounded critics during the UK broadcast of Elizabeth Is Missing in late 2019. “Glenda Jackson shines in this heartrending whodunnit” (The Guardian); “Jackson gave one of the performances of her lifetime” (The Daily Telegraph); “Jackson is remarkable” (The Independent); “a devastatingly real performance” (The Times); “brilliant” (Radio Times).

Glenda Jackson in 2019, when the show first aired, was 83 years old.  She is remembered for her role as Alex Greville in  Sunday Bloody Sunday which was made in 1971 when she was a mere 35 years of age.

Watching   her as Maud Horsham struggle against the onset of Alzheimer’s can be profoundly upsetting.  Some of our friends could not sleep after watching the drama.  “Will this happen to me?”  is a scary question.  Just as real as her studied and accurate performance are the reactions of those who care for her:  her daughter and her grand-daughter.

If you want to see superb acting, DO NOT MISS!