Not what I anticipated after the 30 minute mark.

Rating: 5/10 (10 September 2018)

1) I never believed Caleb was AI.
2) I was fairly certain that Ava was the most advanced AI and was capable of everything she ended up doing.
3) Nathan's behavior was inconsistent. Genius inventor but couldn't predict AI would kill him (never programming in safeguards). Power weightlifter but very heavy drinker. Immediately wanting to start bromance with Caleb.
4) I hypothesized at roughly the 30 minute mark that Nathan was AI. The Turing Test was passed because Caleb never realized it.
5) The original Nathan (killed by Ava sometime back) had earlier programmed an Ava advanced enough to kill her creator, build Nathan II, arrange Caleb's presence and create an escape plan to leave the site. In other words, she was either programmed too well or AI evolved without biological input.
6) Once the Turing Test was passed (Caleb never guessing that Nathan was AI) , Ava (artificially) knew it was safe to enter the outside world and escape detection that she was AI.
I think my version is better than the script writer's end product.