Lynne Reid Banks

In this third book about Omri and his magic cupboard, Omri and hisfriend Patrick must risk grownups' discovering their secret when they find themselves in need of a friend's toy plastic doctors to save wonded people from the dangerous world of the Old West which the cupboard enables them to enter.

A year after he sends his Indian friend, Little Bear, back into the magic cupboard, Omri decides to bring him back only to find that he is close to death and in need of help.