In episode two Quinn asked Carrie to show him video footage of the attack, explaining that he does not remember it.
Carrie showed him how terrorists used him as a test subject for a nerve gas, leaving his life hanging in the balance at the end of season five.
Although he had been given an antidote, Quinn was hospitalised and suffered a major stroke.
His condition worsened after Carrie and Saul convinced doctors to bring him out of a medically-induced coma to quiz him about the attackers’ location.
In the closing scenes of the season five finale, Carrie held a pillow over Quinn, seemingly about to smother him in a mercy killing.
Many fans assumed that Quinn had finally met his end after many close calls throughout the series.
Homeland season six has revealed that Quinn is alive
Carrie almost smothered Quinn in season five
Carrie, Quinn and Saul all return for season six
But as season six has revealed the gas attack has left Quinn’s mind and body damaged, and he is now being looked after in a care facility for veterans.
Rupert Friend, who plays Quinn, explained to Entertainment Weekly: “It’s been nine months, he’s done all the counselling and the tests and the physical [therapy], he’s come to terms with himself.”
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So far the assassin has been seen struggling with what appears to be Post Traumatic Stress Disorder (PTSD), and was caught smoking crack and sleeping with prostitutes.
Season six will explore the concept of “the modern returning soldier, Friend said.
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“I saw this as an opportunity to explore something that’s under-explored in our popular narratives — which is a modern returning soldier. Not with fanfare and streamers, like maybe it was 100 or 50 years ago,” he told Entertainment Weekly.
“Modern warfare spits veterans out and forgets about them. Veterans are coming home to us with diseases, ailments, and inabilities that we’re not even really qualified to deal with. “
Friend teased that the rest of season six will explore “the altered perception of reality that Quinn has, which is fascinating and scary.”
He added: “His misreading of normal and simple situations is going to be a huge problem for him and is going to cause him to entangle himself into complicated and dangerous situations.”