What drives one person to become obsessed with another

Someone they may never even have met? And what happens when the obsessions of unbalanced misfits, desperate loners and aggrieved ex-partners spiral out of control? Stalking is on the increase - and it isn't only celebrities who become the targets of irrational individuals. Men and women with everyday jobs who lead ordinary lives can just as easily become someone else's obsession.

Victims and the phenomenon

Each year, hundreds of people fall victim to terrifying harassment by people they may have never met. Richard Gallagher has researched this disturbing phenomenon to provide a serious investigation into this unsettling but intriguing crime. Featuring interviews with victims, police, psychologists - and those who "stalk stalkers" - he has unearthed accounts of obsession and delusion.