Aged 42 and a teacher for more than 15 years, she works at a comprehensive in a big town on the south coast. The school is doing fine. Its teachers are working well to get the best out of a reasonably nice bunch of kids - all except Susanna. To her, the children are hand grenades with loose pins. They are primed to go off, and they always explode when they are with her. And it's never her fault.
Ted Parkins is head of Susanna's department and in charge of professional development for the whole school. He has worked with her for three years and knows she is a problem that has been ignored for too long. He wants to help, but he's taken to hiding from her when she has a free period. If he doesn't, Susanna will corner him and overwhelm him with the crimes the children have committed that day.
She will complain that "they touched the classroom curtains, and only I am allowed to touch them". Or that a child, clearly plotting to disrupt the lesson, was chattering at the back. "And you know I have to have total silence when I teach." Sometimes Susanna is so tense when telling these tales that her words come out wrong.
Ted and the other heads of department are often presented with pages and pages of notes detailing which children have behaved badly, in exactly what way, and how many times they have done so in the past. It seems to make no difference when Ted points out that these children do not misbehave in other teachers' lessons.
Thanks to her long service at the school, Susanna was put in charge of careers advice a few years ago. It was the wrong decision. When pupils need practical help with where their lives are going - when they are choosing their A-levels, for example - Susanna is not there for them. The stress of being in the spotlight is too much for her. She exhausts her colleagues with her complaints, and communicates nothing to the teenagers, who sense that all she expects from them is bad behaviour. And then she goes off sick. That is where she is now, Ted having persuaded her to taketime off for stress.
He plans to call in the local authority behaviour support services in the hope that Susanna can be helped. She is hard-working and always well prepared for her lessons, but Ted suspects that she will ultimately have to leave. The fundamental issue, he thinks, is that she is scared of the children. Her way of coping is to impose ridiculous rules - rules which she expects them to break.
"Teaching is like learning to drive," Ted says. "At first you notice every little thing, but then you learn to filter it out. Susanna has never acquired that skill. She notices anything that is even slightly out of order and takes it personally. How can people be prepared to be so miserable?" Can Susanna be helped? And can Ted be helped to do it? Mel Myers is a former senior educational psychologist turned reflective practice consultant who works for universities and local authorities. He and his colleague, Sue Clark, specialise in the "interpersonal" skills people and organisations need in order to cope with difficult situations.
Susanna may be scared of children, says Myers, but "it is also a safe bet that she is one of those people who has developed an utterly inappropriate way of communicating with others".
The way we react to each other is extremely hard to change, and can become as ingrained as the instinct that ties our shoelaces. However, we have more chance of modifying our own behaviour than of changing someone else's, he says, and the skill lies in helping someone like Susanna to do just that.
Unfortunately, it is a skill in short supply. "People can be frightened of telling others what they are doing wrong," says Mr Myers. "They start by telling the person how wonderful they are, what talent they have. But most of us are smart enough to see through that."
What is needed, he says, is a person who can tell it straight, who isn't vengeful, isn't bound by received wisdom about what you can or cannot say in a situation like this. They can then establish a dialogue and involve the problem teacher in finding a way forward.
The names of the teachers have been changed. Mel Myers can be contacted on e-mail: firstname.lastname@example.org