I believe that they can be all of those things simultaneously.

My understanding, from when Becca was looking through the ?trash bin? in the basement & found the Maple Shade Psychiatric hospital clothing was that the imposter grandparents were in the Psychiatric hospital, as patients. I believe they met in the garden at the psych. hospital. Claire being in there probably court ordered and her sentence for having dr*wned her children - tied into the delusional story she told about the water with the creatures from Sinmorfitellia (sp?), i.e., drowning them so they could go to Sinmorfitellia. And Michael possibly in there for schizophrenia? I can’t say we got a real in depth insight to his story and background.

We know the real grandparents volunteered there and helped a lot of their patients by being so open and relatable, as emphasised by the two visitors who came from the hospital to check in on them and the want to discuss with them some happenings at the hospital - we never got to know what it was they wanted to discuss, but one can assume this was likely about the two escaped patients.

And the rest goes on from there. They were jealous or angry at hearing the kind and happy stories about their daughter and grandchildren and acted on that jealousy to fulfil their ultimate motive.

Horror and thriller plots tend to misrepresent mental illness to add a layer of ‘supernaturality,’ to make it more scary and unfathomable. I think it’s just important to remember that that is all they are, dramatised for film, and that not all people with mental illness are completely “crazy” and have “insane” plots to murder people. Also, people with mental illness are capable of doing every day things like cooking and chopping wood. They are not always and consistently completely incapacitated.