Set in the early 21st century, the book opens with Johnny Mackintosh living in a children's home (Ben Halader House) located in the fictional Castle Dudbury New Town in the county of Essex, United Kingdom. He has written a
SETI-style program for the children's home's computers and, at the beginning of the book, an alien signal is detected. As the book develops Johnny Mackintosh is abducted by aliens and travels to the centre of the Galaxy, before returning to Earth, but in the distant past. He witnesses the
extinction of the dinosaurs and the destruction of
Atlantis, before returning to the present day and discovering the truth about his parents. The
Spirit of London of the title is the name of the spaceship acquired by Johnny Mackintosh during the course of the book. From the outside it appears identical to the skyscraper situated at 30 St Mary Axe in London, known as '
the Gherkin'. ==Publishing history==