Before mum died, she told Sam that she would always be with him.

On the day of mum's cremation, his sister Becky receives a text from a friend: 'Thinking about you.

X'. Sam becomes convinced that the text is from their mother.

Imagine if he could text back! When he finds mum's mobile phone and a 'contact number' in her handwriting, Sam his heart pounding, sends a message.

It is received by a kind but lonely lorry driver, Tony.

Unthinkingly, Tony responds. Before he knows it, the boy is texting regularly, and Tony is replying.

Sam thinks he's in contact with mum and forms a plan.

He's going to find her and bring her back for Christmas.

By the time Tony realises what's happening, he can't bring himself to tell Sam that it's not his mother on the end of the phone, but neither can he just stop texting or, worse, let the child turn up.

He also realises that he's come to rely on Sam's messages because they make him feel less alone.

As Sam sets out on his journey, Tony must try to find him.

But how will he explain to this little boy that his mother is really dead? And how will Sam cope when confronted with the truth?