"What was it your father wanted you to do?" asks the psychiatrist. "He wants me to die for your sins," says the unhappy one.
This is enough to get him transferred to the local psychiatric unit. But his arrival causes some consternation among the admissions staff. "We've got another son of God," warns one of them. "Keep him away from Tam. They're both big lads, if you know what I mean - no one likes to find out they're not the true redeemer."
Welcome to Muirpark Hospital, the fictitious setting for Psychos, a new television drama series set in the hospital's psychiatric ward. It's a place of monumental shouting matches, deep depression, erratic behaviour, drugs and insults - and that's just among the staff. The grim Seventies wallpaper and horrible settees have an authentically institutional look about them. However, it's not just the setting that rings true. It is, unlike many medical dramas, extraordinarily realistic, according to one of the cast who should know what he's talking about. Iain Fraser, who plays staff nurse Jim Reid, is uniquely qualified to make this judgement, because he spent three and a half years as a psychiatric nurse before training as an actor.
"Unless you've worked in a mental hospital or a psychiatric unit you don't realise that it's always the most unbelievable things that happen," he says. And the fact that some of the doctors seem crazier than some of the patients is not mere chance. "On the ward itself there are very few tantrums - it does happen, but to show it all the time would be making a mockery of the illnesses. A lot of people are very quiet because of their medication."
It's a different story in the staff room, however. "I'll get the popcorn," quips one of the office staff, as two psychiatrists retreat to an empty room for a loud and angry row. And when they aren't shouting at each other, the humour is acerbic to say the least. "It's hysterical being a nurse," says Iain Fraser. "There are some very funny situations. It's not taking the mickey out of the patients, but it's the situations that you find yourself in because of the people you're dealing with, and not to show the funny side wouldn't give the complete picture."
Fraser, 30, from Stenhousemuir in Scotland, worked on an admissions ward for male patients suffering from psycho-geriatric disorders, Alzheimer's disease, schizophrenia and other mental illnesses. "The early shift was the hardest because you have to get the patients up," he says.
Sometimes, he says, there is no getting round the fact that patients need to be physically restrained. "In Psychos there are some scenes with people getting hauled around, because that does happen." But mostly, he says, the simple presence of the nurse is calming enough. "It's all down to presence. You make sure that you're in front of them, touch their arm or something, get their attention and ask them to stop. There was one guy who had obsessive-compulsive disorder, and he would copy whatever he saw on the TV. Like if he saw someone pouring water, he would start pouring things from one container to another - like other people's cups of tea, which would drive the other people mental. The nurses would come in and just calm everything down."
Nurses, he says, have to cultivate professional coolness. "If you don't then you won't be able to cope. But a death is worse if you actually knew the patient quite well. You wouldn't be human if it didn't affect you in some way."
Nursing is excellent training for acting, he says. "It gives you insight. You're improvising every day of your life around the people that you meet and the things you have to deal with, whereas in drama school you just have a script and you know what to do," he says. This can lead to some novel ways of dealing with patients - like one who kept running away and had to be physically brought back to the ward by the nursing staff.
"The next time he went off I got an empty wallet and a suitcase and put it by the door. Then I ran after him and got in front of him and said, 'Willy, where are you going?' and he said, 'I'm fed up with this bloody place, I'm on my way home' and I said, 'Well, you're away without your wallet, and it's empty because your money's in the office, and look at your suitcase, it's just lying by the door' and the two of us walked back without any bother."
Fraser didn't take his final nursing exams because he decided it was time to move on to the Royal Scottish Academy of Music and Drama. "In a way I felt sorry about that, though I'd always known since school that I wanted to be an actor." Both his father and sister worked in the nursing profession. "Nursing was a means of killing time before I went to drama school - I didn't want to go till I was 25. You've had a bit of experience of other things. I'd always planned to go there, since school - it was a wee bit unheard of because everyone else wanted to be a footballer."
When he went to the casting session for Psychos, he was asked what he had done before. "I just started laughing. When I said I'd been a psychiatric nurse they asked me what I thought of the script. When I first read it, I thought, 'At last someone has nailed what it's really like - this guy must have been a doctor'. It was uncanny the similarity between Jim Reid, my character, and me - right nationality, right background. So I was convinced they'd probably give it to someone from Croydon who'd have to put the accent on."
Any would-be psychiatric nurses who don't plan to move into showbusiness could do worse than watch the show, he says. "I wouldn't be doing it if it wasn't realistic. For the first time they are showing what it's really like in a psychiatric hospital."
'Psychos' begins Thursday 6 May at 10pm on Channel 4.