I can’t help it. They’re all beginning to run together in my head. How many post-apocalyptic stories featuring hot young stars as the brave teen heroes who are the only ones who can save the day for freedom and middle aged, classically trained actors as the totalitarian villains trying to stop them can we have?

At some point, I forget which one has Meryl Streep (“The Giver”), which one has Julianne Moore (“The Hunger Games”), which one has Patricia Clarkson (“Maze Runner”), and which one has Kate Winslet and Naomi Watts (“The Divergent Series”). When this latest and second-to-last installment of the “Divergent” series has its lead characters scaling an enormous wall in response to a message from an entirely unknown source outside (like “Maze Runner”) and the romance heats up (“Hunger Games”) and another distinguished actor shows up to explain what is going on (“The Giver”), the narratives all sort of begin to merge.

So, let’s try to get it straight. “Divergent” is the one where a post-apocalyptic Chicago had genetically modified its inhabitants so that they each had one strength: compassion, intelligence, courage, honesty, and peacefulness. At age 16, each person is tested and assigned to the appropriate faction. He or she must leave the family; the faction is the family now. The test reveals that Beatrice “Tris” Prior (Shailene Woodley) is “divergent,” with multiple strengths. That makes her a threat to the system and to the people who control it, led by Jeanine (Kate Winslet), who was killed at the end of the last chapter. As this film begins, Tris and Four (Theo James) are deciding what to do about a message calling on them to leave Chicago to find out more about what role the Divergents can play to solve the problems that led to the creation of the faction system. Tris believes she must answer the invitation, but Four worries that it could be a trap.

Four’s mother, Evelyn (Naomi Watts), formerly a leader of the rebel forces, is now beginning to show Jeannine-like tendencies (yes, this is a lot like “Hunger Games”), allowing public executions. She tells Four, her long-estranged son, she is doing it for him, but he sees what she is doing as yet another betrayal.

Tris and Four make it beyond the wall (an extreme version of rappelling is the film’s best action sequence and the only one to match the adrenalin-surge and dynamism of the earlier film’s zip-wire scene) and, behind a digital “camo wall” find a community of “pures,” non-genetically modified people, led by David (Jeff Daniels), who explains in near-folksy genial terms that Chicago was an experiment and its inhabitants were constantly monitored, somewhere between lab rats and “The Truman Show.” Meanwhile, Four, her brother Caleb (Ansel Elgort) and her friends have been assigned to either monitor or fight (with some cool new drone gear).

There are some fancy visuals but as with the earlier chapters no special effects are close to the impact of Woodley’s hazel-colored doe eyes or James’ smoulder. And there’s a bright spot when we meet a new character, Matthew, sympathetically played by Bill Skarsgård, who looks more like the younger brother of “Madame Secretary’s” Erich Bergen than the real-life brother of the various handsome members of the Skarsgård family.

But the plot is overly complicated on the surface, padded (really, can we stop turning three books into four movies?), confusing, and unsatisfying, without the exhilaration we felt as Tris discovered and deployed her power in the first two. She spends too much time in a room listening to David, and a visit to Providence for a meeting with the Council is poorly handled. If this movie had a faction, it would be: placeholder until the last chapter.

Parents should know that this film includes extensive sci-fi/action violence with guns, explosions, and crashes, with many characters injured and killed, brief strong language, and non-explicit nudity in shadow.

Family discussion: Why did Evelyn think she had to use force, despite what had happened before? How did Four and Triss look at the invitation from outside the wall differently? Why did David lie?

If you like this, try: the earlier films in the series and the “Hunger Games” and “Maze Runner” films