Anxiety, a small bout of depression or an obsessional thought – all of us can have these feelings at some time, but what if these persist and take over our life? In the UK, one in four people will suffer from some form of mental health problem every year. What causes it differs for every one of us: our genes, lifestyle or events from the past can all play a part. But whatever the trigger, mental illness can happen to anyone, at any time. Using computer graphics to travel inside the body, this film explores the science behind mental illness, discovering the social, biological and psychological changes that happen to five people suffering from different mental health disorders and unraveling the treatments that are helping them overcome their conditions.