I just finished watching this film.
Very clever, if a bit too obscure, apparently, for folks watching it.
Here's what I believe was going on. . .
First of all, Maggie was absolutely not from the future.
She was a military/CIA/psyops mind control puppet being used to set up small paramilitary/cult organizations all over the country. (Such things exist; research "Greenbaum" if you're interested).
The methods of cult creation were being followed by the book; sequestering of knowledge, controlled tests of loyalty and various mind games perpetrated on the victims, absolute control over who stays and who goes, punishing questions, and starving victims so as to lower their natural psychological and physical defenses. (A person genuinely interested in elevating people would absolutely NOT use any of these techniques, but would rather encourage the accumulation of knowledge and personal power and self-determinism). They were looking to create groups of people who were docile and obedient, then train them for terrorist-like activities which would no-doubt not be carried out without question. Such people are perfect for later 'use' by secret government initiatives. The network of cults and controlled people would be at this point (both in the story's history, and out here in reality), widespread and well-funded and highly resourced.
The drugged child was almost certainly a product of the same network of cult activity; parents who had been sucked in and who had conceived under direction and who had given up the child to the secret group. The girl was being programmed to fulfill another such roll, probably much like Maggie had been, possibly an in vitro-fertilized clone or similar.
Maggie had been heavily programmed, personality split for multiple purposes, mind-wiped and then activated for use. Her handler was the old beardy guy with the John Lennon glasses, and he too was no-doubt being controlled through his handler, though we never see that person. Such systems are endlessly subdivided in this manner so that the whole network is controlled by only a few individuals at the top.
The FBI investigator was well aware of what she was up against, hence the incredible anxiety and precautions against monitoring. (If she was searching for bugs and listening devices in a hotel room, then she suspected people in her own organization being in on the Shadow Government side; who else would know where she was going and what room she would be in?)
The point of these cult networks is to place highly controlled Manchurian Candidate types in positions of power peppered throughout all levels of society. That's the reason such systems exist.
The photograph of Maggie at a wedding out in the open gave the viewer proof that her story was not true; she had a life before the bathtub, though she might not know it in her active personality.
The secret handshake was programmed into the child, and would be used as a proof positive to convince the other victims of the authenticity of Maggie's story.
Other items of interest: there was a brief flash in the first basement scene of another child slipping into Maggie's room. We never see that kid again.
The air tank was clearly a theatrical ruse, because Maggie was later revealed to be a smoker. I don't understand that part. Why reveal that?
I didn't understand the purpose behind the blood transfusions. Perhaps just more theater for the benefit of the victims.
Anyway, these were just the ideas which smacked me while I was watching this. If this is part of a trilogy, then it would be interesting to see what other ideas the film's creative staff have in mind.
Whatever the case, this whole story stunk high of evil. Very creepy, but also very well informed. I would prefer it if there had been more open discussion as to the true nature of this story. This kind of stuff really happens, and people would benefit from having their eyes open.