Five footprints are the only sign that Daniel Buck was ever here. 

Yesterday they were a family just like any other: Anna and James, and their little boy, Daniel.

But in one careless moment everything changed.

A front door accidentally left ajar . . . and Daniel was gone.

Now they are a pair of strangers who can't even look each other in the eye.

Distrust and unspoken words fill the void where their son used to be.

Anna will go to any lengths to find Daniel - a four-year-old doesn't just vanish into thin air. But how far will this desperate search push her?

Right to the brink.

And beyond.