Having worked with young children I was fascinated to read this story and can recognise a lot of youngsters I've encountered in the three children. The author has changed her style considerably in the rewritten first chapter and the whole feel of this is different to the rest of the work. I have rated the writing style and pace on chapter one only but the rest of the review relates to the full text.

Tristan is a very believable character and is rounding out nicely during the story. He is, perhaps, a little cerebral in the cave but his fearlessness going through the squeeze and in the darkness is something I have seen for myself, children go at these things like rats up a drainpipe!
Sebastian is very well observed and for me his logic is priceless. The research that has gone into this portrayal is obvious and the possibilities of the relationship almost endless. I look forward to introducing the edited work to my children.

Some more thought needs to be given to the title. It explains the story and gives scope to expand the book into a series but somehow it seems a little old fashioned. I wish I could offer some help on that point, maybe somebody else will.

Overall an interesting piece of writing which should appeal to the target age group.