The way I see it.... *SPOILERS*

Seems very obvious.


Molly did the opening murders while in a schizo state. She blocked it out when 'normal'.
The 'hand' was simply one of her victims trying to get onboard, OR MORE LIKELY it was a false recollection by the 'normal' Molly to mentally back-up her belief there was another killer.

She also kills the new victims, again when she is her killer self.

The Professor is wrongly executed for the new murders.

The only 'twist' at the very end is that the assumption we make about Molly getting away with it and starting a new life for her killer self.
She DID get away with the killings (as The Prof is found guilty) but she had not gone and started a new life, as it turns out those scenes were simply the delusion of her killer side.

In reality...the 'normal' Molly woke up in an asylum. Only her 'other self' really 'escaped', but that 'other' Molly only escaped via a delusion.
Normal Molly, along with her physical body of course, was really locked away in an asylum.







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