Mr Huff shows us what can happen when you let negative thoughts take over. We see how a bad day can get worse or better depending on how you think about it.
As negative thoughts take hold of our young, anxious protagonist, Bill, we see the Mr Huff shadow grow bigger, darker and more dominant.
Walker takes us through the various things Bill tries to do to get rid of Mr Huff - he waits, he ignores, he tries to be brave, but none of these things really work and Mr Huff keeps getting bigger.
It looks like Mr Huff might be around forever.
Until, Bill suddenly stops. He looks at Mr Huff and he sees himself inside Mr Huff's tears.
At this point, I'm not sure if Bill is embracing his own sadness or seeing himself as others see him or responding empathically to someone else's sadness. Maybe it's all three.
However. it's enough to make a difference.
Bill looks up and around and begins to take notice of all the little things around him. He observes others dealing with the same day differently to himself and slowly, little by little, he begins to get involved with those around him.
And with every little thing that Bill does - from smiling at people, to talking and joining in, Mr Huff gradually gets smaller and smaller.
I loved Walker's previous book, Peggy, which was shortlisted for the CBCA Early Childhood book back in 2013.
There is something about the sensitivity and quirkiness of her books that appeal to young children (and their adult readers alike). Her pencil, ink and collage illustration are attractive and engaging. They subtly convey the various moods within the story.
When Mr Huff was first launched, an exhibition of Walker's collages was held at the No Vacancy Project Space in Federation Square.
Sadly the exhibition is now finished, but you can see some images of what looked like an amazing display here.
My CBCA shortlist post is here.