Arthur is just an regular kid however, like in the previous four books of the series, he is thrown into another adventure in a place called the Secondary realm (a realm that runs parallel to the real world) where he must claim the fifth magical key from another powerful being of that realm. Arthur is just an ordinary schoolboy that, more than ever, just wants to return to his normal life. Unfortunately, in this fifth book in the Keys to the Kingdom series, Arthur is getting more deeply entangled in the power struggles between the various beings that live in the realm called the Secondary realm, a world which lies parallel to the real world. Arthur has been given the role as heir to the Secondary Realm by its previous ruler, called the Architect. In order for Arthur to claim rule over the Secondary Realms, he must collect seven magical keys in total from seven powerful beings that currently rule the different domains of the Secondary Realm. He must also find the seven parts of the Architect's Will. The Will has been made sentient and split up into seven magical animals. So far, Arthur has collected four keys from beings called Mister Monday, Grim Tuesday, Drowned Wednesday and Sir Thursday as well as the four parts of the Will that were under the care of these beings. The sentient portions of the Will have combined to form one powerful and fussy/bossy being who calls herself Dame Primus and helps Arthur on each leg of his quest.
After his fourth adventure in which he subdued a powerful army commander called Sir Thursday and claimed his magical key and the fourth part of the Will, Arthur finds out that everywhere in the Secondary Realms, there is chaos and instability. Arthur would like to go home and rest, however, he learns that the doorways out of the Secondary Realm and into his own world have been shut down. Arthur is concerned about his friend Leaf, who, last he heard, had been fighting his doppelganger, a creature that had been spreading an insidious mind-controlling mold in his world. Arthur wants to go home and see that everyone, his family and friends, are okay. Arthur finds out that everyone, including Leaf has been taken to another powerful being's domain. The being calls herself Lady Friday and sends Arthur a letter saying that he and any other being that claims to be an Heir to the Secondary Realm are free to come to her domain and find the fifth magical key as well as the fifth portion of the Will. When Arthur touches the silver plate that came with the letter he is immediately transported to Lady Friday's domain.
Meanwhile, Leaf wakes up and finds herself in a hospital that has been moved to the Secondary Realm. The people in the hospital claim to work for Lady Friday and they are in charge of turning the sleeping hospital patients and/or commanding a patient to sleep-walk to Lady Friday where she will use them for a nefarious purpose. As Leaf is busy figuring out what Lady Friday is using the patients for, Arthur arrives at the fringes of Lady Friday's domain. He meets a few pre-occupied beings of the Secondary Realm and they tell him how to get to Lady Friday's Scriptorium, which is apparently where she's keeping the fifth key. Suddenly, two of Arthur's friends, Suzy and Fred appear. Arthur is not sure whether she can trust them because they are "Piper's Children" or children that can be controlled by the Piper's song. The Piper is one of the powerful beings that claims to be a true heir to the Secondary Realm and he escaped Arthur's grasp in the fourth book. Suzy and Fred are be-spelled by the Piper, however the Piper never ordered them to do any harm to Arthur so for now they are safe. The Piper had also received a letter from Lady Friday and Suzy and Fred had touched the silver plate to transport themselves to where they knew Arthur would also be.
Leaf finds out that Lady Friday keeps the sleeping patients so that she can absorb and experience their lives - she literally drinks in their thoughts and memories, leaving behind a husk of a person that never wakes up. Lady Friday sees Leaf and reveals to her that she is using Leaf as bait to get Arthur into her domain. In order to force Leaf to do what she's told, Lady Friday threatens to absorb her Aunt Mango's memories as well. Leaf tries to send a message to Dame Primus and her headquarters however she is caught and put to sleep by one of Lady Friday's minions.
Meanwhile, Arthur makes his way to Lady Friday's Scriptorium. Along the way, he and his friends are caught up in a brief battle between winged and silent beings called Winged Servants and other winged beings called Artful Loungers. The WInged Servants normally work for Lady Friday and Lady Friday is resisting another being called Superior Saturday who commands the Artful Loungers. But Lady Friday seems to have abandoned her citizens so Arthur and his friends help the Winged Servants fight off the Artful Loungers, In return, the Winged Servants help him by grabbing onto Arthur and his friends and fly them up to the center of Lady Friday's domain. As they make their way there, Arthur amasses the allegiance more and more of Lady Friday's citizens and minions, who have lost hope that Lady Friday and protect them from Superior Saturday. Arthur knows that Lady Friday plans on getting him, the Piper and any other heir claimant to pick each other off in their fight for the fifth key. So, instead of going where she expects everyone to gather, he goes off to find the fifth part of the sentient Will, thinking that this will give him a magical advantage. After he finds the fifth part of the Will, Arthur and his friends look for the fifth key. When they find the fifth key, they also find the Piper. One of the Piper's minions touches the fifth key and activates a trap as a vortex of Nothing starts to expand. Nothing is like anti-matter as it destroys everything living.
Meanwhile, Leaf awakens to the fact that Lady Friday has gone mad and wants to experience all the sleeping patients at once. Leaf is afraid her Aunt Mango will be taken and she rushes off to save her. Arthur had given her a disc that used to belong to a man named Captain Tom, a mariner that Arthur had met while on his adventure to obtain the second key from Grim Tuesday. Arthur had befriended this mariner and the mariner had given Arthur the disc so that Arthur may call upon his help whenever he is in need. Arthur had given the disc to Leaf and Leaf had willed the Captain to appear. The Captain makes his appearance and Arthur and his friends also appear just in time to stop Lady Friday from experiencing all the sleeping patients. Arthur claims the fifth key. At the end of the story, he finds a scrap of paper from Superior Saturday who reveals that she has a master plan to take over the Secondary Realms.
Best part of story, including ending:
I like the interesting concept of experiencing other people's memories and feelings and how these things are actually considered commodities by the beings of the Secondary Realms.
Best scene in story:
My favorite scene is when Arthur finds the fifth part of the will and learns that Dame Primus may be unstable without it. It is interesting that there are hints that Dame Primus might let the power of being the trustee of Arthur's magical Keys get to her head.
Opinion about the main character:
I like that Arthur is reluctant for the citizens of the Secondary Realm to get hurt, even if they appear to be on the enemy's side.