After Johnny Maxwell, a boy in his early teens, finds Mrs. Tachyon, an old bag lady, by a cinema he discovers that her trolley is in fact a time machine. He goes back to his town, Blackbury, during the time of The Blitz with his friends Stephen, Bigmac, Kirsty and Yo-less. Wobbler gets left behind in 1941, and when they return for him, Johnny tries to prevent the deaths caused in the raid.
The gang
Johnny Maxwell - Johnny is the protagonist. Stephen 'Wobbler' Johnson - Johnny's best friend and the second main character in the book. He is overweight and heavily into computers, an expert at piracy. He wants to be a "nerd", but they would not let him join. It is his considered opinion that Johnny is mental. His real name is Stephen Johnson. In Johnny and the Bomb, Wobbler gets stuck in 1941 and grows up to be a billionaire calling himself Sir John and Bigmac is locked up in the Tower of London as a Nazi spy, but, due to the time travel and multiple timelines involved, where and if this happens is questionable. Wobbler returns successfully from 1941 and Bigmac is free from the Tower of London. Simon 'Bigmac' Wrigley. - An asthmatic skinhead who is deeply embarrassed by his interest in maths. He lives with his brother in a rundown tower block on the edge of Blackbury. He is not exactly a criminal but has a confused grasp of car ownership. His real name is Simon Wrigley. Yo-less - A West Indian boy, nicknamed by Johnny because he does not say "Yo!" His interests include Star Trek, train spotting, Morris dancing, and brass band music. His reaction to those who are surprised a black kid has such "uncool" hobbies varies from amusement to irritation. When faced with genuine racism he has a brittle anger that manifests itself in cold, almost emotionlessly delivered sarcasm. Kirsty - Unlike the rest of the gang, Kirsty is a highly organised person who knows exactly where she wants to go in life. She is highly intelligent but has very poor people skills, something she views as a character flaw in everyone else. She is trying to get Johnny's life organised since he is clearly incapable of doing it himself, but has not realised that he does not especially want his life organised. He finds her very easy to talk to since she never listens. She is the only female member of the gang.
In the book, Johnny changes history so that no-one dies in the Paradise Street bombing. However, the TV series has this as the original history, which the gang inadvertently changes on their first visit to the past. In the history thus created, Simon was jailed in the Tower of London for being a Nazi spy though he is later released; Johnny's grandmother was killed, meaning he no longer exists. When Johnny faces his own grandfather, he mistakes him for an intruder. She is then saved due to the alarm going off and Johnny exists again. A smaller change is that in the series, Stephen is renamed Walter, later Sir Walter.
