In this episode, Matthew tells two stories, both of which raise profound questions about how we think. A group of terrified teenagers discover a disturbing app on social media. A world renowned doctor sets out to uncover hidden crimes.

The tragic events Matthew examines lead to a mother getting jailed for killing her two children. The key piece of testimony in her trial hinges on a question of statistical probability. But, as Matthew reveals, human beings are extremely poor at understanding the improbable.

Producer: Gemma Newby Music, Sound Design and Mix: Benbrick Series Editor: Russell Finch Executive Producer: Sean Glynn and Max O'Brien

Sideways is produced by Novel for BBC Radio 4