The second book in the series was published in paperback by Avon books, now an imprint of HarperCollins Publishers. It was a New York Times Notable Book. It was illustrated at least by Bill Geldart, William Coldart (UK), and Piers Sanford (later).
Omri and Patrick intervene aggressively in Little Bear's home world, Kirkus observed in contrast to the first book. "Feisty, likable characters and the precise logic by which Banks evolves events from her premises make this one of the better recent fantasies. Readers, enjoying the action and adventure, may also ponder its moral dilemmas."
One day Omri receives a letter announcing that he has won first prize in a story-writing competition for his tale "The Plastic Indian" (actually a recount of everything that happened in the first book; everyone else assumes that Omri's story is fictional.) Wanting to share his good news, Omri brings Little Bear and his wife, Bright Stars, back through the magic cupboard. However Omri sees right away that Little Bear has been badly wounded by French soldiers. To make matters worse, Tommy, the World War I medic, has died since the events in the previous novel.
Omri confronts Patrick again, and Patrick accepts that the magic and the little people are real once more. Patrick shows Omri a set of plastic figures that his cousin Tamsin recently received as a birthday present; it includes a modern surgical team. They intend to sneak out with the group and bring them to life in the cupboard, but Tamsin catches the boys on the way out and Omri is only able to retain one of the figures.
On the train home, Omri sees that he has taken the nurse from Tamsin's set. Seeing this as better than nothing, he and Patrick put the nurse in the cupboard and bring her to life. The nurse, called Matron is led to believe that she is dreaming and saves Little Bear's life through careful operation. Matron also announces that Bright Stars is pregnant and the boys decide that they will bring her again when the baby is born.
As Little Bear recovers, Patrick brings back his old friend Boone through the cupboard. When Boone talks about ways to help Little Bear's people, Patrick gets the idea to take plastic soldiers (with modern weaponry) back through the cupboard to Little Bear's time. Little Bear likes the idea of using new weapons (he now calls them "now-guns") but wants to only take fellow Iroquois warriors with him. So the boys buy several more plastic figures from the local shops and bring them all forward with the cupboard. They also recruit a miniature Royal Marine corporal (later sergeant) named Fickets to instruct the Iroquois in weapons usage.
After Little Bear and his troops are sent back, the boys express a desire to go back themselves. A casual comment by Boone prompts Omri and Patrick to wonder if it is merely the key which is magical and not the cupboard — meaning that if they found something big enough they could indeed go back. Using a large chest he recently acquired, Omri is sent back and inhabits a drawing on Little Bear's teepee. Omri witnesses a group of Little Bear's enemies, the Algonquins attacking the village, and he is nearly burned to death before Patrick brings him back. He bears a few scars from this encounter and is visibly shaken. Later that night Patrick brings the Iroquois back only to find that they were completely unprepared for the use of modern weapons and their numbers have been decimated; their unfamiliarity with the power of the weapons resulting in them surrounding their enemies and shooting without realizing how far the shots would travel, with some of them being shot by their own side by accident. Matron is able to save several lives but many are near death and eight of them have already died. Little Bear feels ashamed of leading his troops into death, but Bright Stars is able to comfort him by showing off their newborn son, whom he names Tall Bear.
As Omri sleeps downstairs, he spots a trio of skinheads breaking into the house and taking a few of his family's possessions. He becomes enraged and brings back their Marine friend Fickets along with a complement of troops to deal with the burglars. Omri, Patrick and the soldiers defeat and scare the skinheads, leaving Omri free of their oppression for good as they are now too scared of him to hurt him any more. As the story concludes, Little Bear learns why Omri originally brought him back to this time, and reflects that his son will be proud to know that his father will live on in Omri's story long after his death.