It begins with a small white lie.

The kind of lie you might tell to keep your child out of trouble - especially when he begs you to confirm that he came home early last night and has been up in his room ever since.

And so you back him up. You give him an alibi. Instead of telling the truth: that he actually crept in at 3 a.m., clothes streaked with mud and bruises on his face. Fear in his eyes and a plea in his voice you've not heard for a long time. Please, Dad.

But sometimes a small white lie can be the most dangerous thing in the world.

Because five teenagers went into the woods last night.

And only four came out . . .