The third book in the series was illustrated at least by Graham Philpot (UK), Ted Lewin (US), and Piers Sanford (later).
Following the previous book, Patrick deeply wants to travel back to Boone's time. Omri agrees to "hide" Patrick's true whereabouts in the large chest he has in his room.
Patrick mistakenly keeps the Boone plastic figure in his pocket during time travel and nearly kills Boone in doing so. Boone is unconscious when Patrick arrives in the Wild West. Patrick manages to find a saloon and meets Ruby Lou. Ruby Lou (and the saloon piano player) helps him find the unconscious Boone.
Meanwhile, Omri gets Patrick's cousin Emma to help by providing more toys. She chooses Ruby Lou as her own "person" to bring to life.
Also Omri is left alone to deal with the consequences of the battle in the last book. Many Indians are seriously injured and nine die despite Matron's best efforts. Due to Patrick's carelessness Boone nearly dies too, but is saved by the combined efforts of Matron and Omri. Thanks to the toys Emma provided Omri, Matron is able to get a surgical team that saves the rest.
Ultimately Omri can't keep Patrick in the past anymore and brings him back using the chest, using its powers to send the Indians back to their own time at the same time. Doing so saves Patrick and Ruby Lou as a tornado was about to kill them, but the tornado is pulled forward through the chest, destroying it, severely damaging the cupboard and sending the key to an unknown location while the tornado wreaks havoc on England. Ruby Lou is pulled forward in time thanks to Emma's toy version of her, but she and Boone are trapped in the cupboard. While Omri manages to repair the cupboard (which inadvertently saves Boone's life), the key is still missing. Boone and Ruby settle in the present and fall in love and want to get married, but also want to return home. One day Omri, by sheer luck, finds the key in the bushes. Omri uses it to summon all of the group's friends for Boone and Ruby Lou's wedding before sending everyone home. Afterwards Omri decides to put the key and cupboard into a safe-deposit box and not use them again, leaving them perhaps for his children, having realized that the power is just too dangerous after everything that has happened.