On Armistice Day 2015, Mel gets a phone call from her son’s school, asking her to come in. When she arrives, she finds the car park filled with ambulances and police cars, emergency services buzzing around.

It began with someone fainting in assembly and then, like dominoes, more teenagers began to collapse. Students were sent back to their classrooms, but the outbreak spread, with more and more people feeling dizzy and sick.

In this episode of Sideways, Matthew Syed tells the story of a strange fainting outbreak at a school and delves into these types of events which affect dozens - sometimes hundreds - of people. What looks unexplained turns out to have a fascinating psychological explanation. But, as Matthew discovers, sometimes our desire to explain things can lead to us explaining them away.

With Professor Sir Simon Wessely, psychiatrist and epidemiologist at Kings College, London and Dr Johanna Braun, artist and researcher at the Academy of Fine Arts, Vienna.

Presenter: Matthew Syed Producer: Pippa Smith Series Editor: Katherine Godfrey Sound Design and Mix: Rob Speight Theme music by Ioana Selaru A Novel production for BBC Radio 4