“Defending Jacob” is an eight-episode murder mystery from Apple TV Plus with a full catalog of twists and an impressive cast that includes Chris Evans, Michelle Dockery, Cherry Jones and J.K. Simmons. It’s also Exhibit A for a question that’s becoming increasingly unavoidable: Why does everything have to be a television series?

The show, whose first three episodes premiere Friday, was created and written by Mark Bomback, who has some high-quality experience in the movies: He was a writer and executive producer of “Dawn of” and “War for” the Planet of the Apes, two of the best thinking-person’s science-fiction action films of recent years.

And in “Defending Jacob,” in which Evans plays a prosecutor whose 14-year-old son is accused of murdering a classmate, Bomback has constructed an entertaining psychological thriller that takes some clever turns. If it had come out in the 1980s or ’90s, when a lot of stories like this did, it might have starred Harrison Ford or Sharon Stone. It definitely would have been around 120 to 150 minutes long.

But Bomback, working with the director Morten Tyldum, has stretched the proceedings out to 400 minutes. And while it means we get to see more of Jones and Simmons — and of the young actor Jaeden Martell, who’s good as the teenage suspect — it’s mostly a case of subtraction by addition.