Mind Flayers are running the Asylum Quest

A mind flayer is feeding of the patients in an asylum.
Will the PCs kill the mind flayer even if all its thralls revert to being insane?

History

Photo provided by State Records NSW

About a hundred years ago, a young half-elf physician named Derrin Urcabae began treating the mentally deficient and insane. As one of the few people in the city who would do so, he soon found himself overwhelmed with patients.

After his death, investigations discovered that Derrin Urcabae used his position and the facilities to perform inhuman experiments on some of the truly mad inmates.
He performed brain surgeries in order to fix the madness and had a special laboratory for this.

Plot Hook

An ally of the PCs is taken to the asylum, and someone close to that ally alerts
the PCs. Or if the PCs are new to the region a person tells them about the asylum and asks to save the people inside.

Streetwise and History checks reveal the history and the corruption in the asylum.

Personnel and Corruption

It's easy to get people committed (2 day observation), and with a bribe of 500 gp
they can be held indefinitely.

A bribe of 1000 gp will get anyone out of the asylum. If an inmate escapes, the guards may use deadly force to stop him.

The administrator of the asylum these days is Kolistra Mahaven, an old woman past her prime.
She runs the asylum to keep it from going down so that the inmates are kept off the streets.
Restoring the asylum  is her priority and she needs a lot of money for that.
So she wants to sell the laboratory and its books.

There are 2 Dwarven brothers as wardens, most of the asylum is decayed as is the brain lab.
Their names are Ersun and Torar Faltek.

There are about 20 patients currently in the asylum.
They are chained in their rooms but reasonably fed and taken care of.

Dark Secrets

Two months ago, the 3 Faltek brothers fought against a mind flayer settlement far under the city. The settlement was destroyed but the eldest brother Nalin was infected by a mind flayer parasite and would turn into a mind flayer soon.

The 2 brothers brought him to the asylum and applied as wardens.
They were hired as no one else wanted the work.
They wanted to use the lab to cure their brother.

Their brother transformed into a complete mind flayer but a fraction of his mind remained.
So he didn't enthrall them or eat their brains.
He told them he was hungry. So they brought him patients to feed on.

The administrator discovered the mind flayer as she secretly followed one of the brothers.
She wants to keep the mind flayer and made him a deal:
free brains in exchange for enthralling patients, freeing them of their mental illness.
Thralls obey the mind flayer completely, the few feelings they have are love for the mind flayer.
If the mind flayer dies, the thralls return to normal.

Relationship Map

Inmates

 

Mental illnesses can be used in a light and humorous tone but mental illnesses are offending to some people, especially when used as stereotypes.

So use the following list with care:

• Someone who thinks he's a king, for example Crazy Jared
• A woman that keeps shouting "I'm the Raven Queen"
• Someone pretending to be a cleric name Steve who worships himself
• sycophant, someone sucking up to people
• compulsive liar
  

Example Encounter

Example Encounter (level 12):

• Mind Flayer infiltrator (Monster Manual; add ability to create thrall)
• Administrator is Human Gladiator (Monster Manual 2)
• 2 Dwarven brothers are Githyanki Mindslicer (Monster Manual)
• 20 Enthralled patients are Horde Ghoul (Monster Manual;remove undead traits)

Aftermath

Some questions after a possible battle:

• If the mindflayer is dead, what will happen to the patients?
• Will the PCs go public with these secrets?
• Will the PCs succeed in curing the mind flayer?
• After all this, will the PCs help rebuild the asylum?
• What about the brain laboratory and books, will the PCs destroy them?

So what do you think about the adventure? 
If there are questions or constructive feedback, just let me know.