The ghoulish masks are out, goblins and witches roam the streets and skeletons dangle in shop windows - this is not a week for those of a nervous disposition. Halloween has become a great commercial opportunity.

It's also prompting more and more warnings, as trick or treat turns nasty, and some Christian groups see a dangerous emphasis on the darker side of the spiritual.

So what's it really about? Why has what was once regarded as a piece of harmless fun involving dunking for apples prompted such alarm? And what's it all got to do with the church festivals of All Souls and All Saints this week? Roy Jenkins and guests discuss the issues.