The Fragile Heart

I watched the first three episodes of The Fragile Heart on Acorn but when I got to the 4th episode, it required me to sign up for Prime Video. I went to my son's house to watch the 4th episode on Prime Video and it required a sign up for Acorn. We have been loyal customers since Comcast began, have basic cable, Acorn and Netflix. How can I view this 4th and final episode without getting another streaming service?