Following on from the events of 'Escape Velocity', the Doctor, Fitz and Anji find themselves back in Earth's prehistoric past encountering, is short order, a dinosaur and a caveman. Since these two are from different periods, it is plain something is wrong. They soon pass through barriers to other time periods, which also show a similar degree of wrongness. What has caused this? And are they even on Earth?
The first new adventure of the Doctor travelling through time and space following the stranded on earth story arc borrows significantly from the past: we have a beginning that looks like the changeover between the first two episodes of the TV series, a world set up not dissimilar to that in 'The War Games', a Doctor without his memories like 'Spearhead from Space', and so forth. And then it borrows from a movie, the name of which I won't reveal to avoid giving away the plot, but it is something-world, too.
So with all these references, how does the book stand up? Very well, thanks. Despite them, the novel is very much itself - its tone is nothing like those it recalls, and Jac Rayner is obviously in control. The story contains a variety of humorous elements, ranging from light to quite black, but the humour doesn't unduly dominate.
Perhaps most importantly, the characters of Fitz and Anji receive a lot of focus. This is Anji's first book as a full-fledged companion, and she wasn't the most sympathetic character in her first appearance. She ends up far more rounded, and the repeated literary device of her composing imaginary emails to her dead boyfriend helps to deepen both her and her now lost relationship.
Fitz has been out of the books for a while, and there are some facts about the character that really haven't been given due attention. This book helps to reintroduce him as a sort-of lovable loser while bringing these difficult facts to the foreground and having them dealt with - for the moment, anyway. With the Doctor still not having fully recovered his memory, Fitz has many more cards in his hand than either of his travelling companions, but needs to be conscious of what gets out as it may force the Doctor back to the state that his century-long recovery on Earth has been meant to heal.
Character driven and with a fun plot, this book is a good read. It is possibly a little overly backwards referencing for it to be a good start for new readers of the series, but regular readers should enjoy it.