Book excerpt: The Doctor and his travelling companion Alice Obiefune never look for trouble… but somehow it always seems to find them. Most recently, they battled their way out of a reality created to entrap them, and even successfully raised the potentially-genocidal tree creature known as the Sapling into a fully-functional, non-murderous adult, through the power of their joint example. Now it’s time for a little jaunt through time, purely as tourists. Surely nothing can go wrong…