Arthur, a regular schoolboy, has been chosen as the heir to a mysterious realm that lies parallel to his own but the beings of that realm will not concede their power to him without a fight. Arthur is just a regular kid living in the suburbs and going to school. One day, however, he meets a being from the Secondary Realm, a realm that runs parallel to the real world. Arthur learns that he has been chosen as the Rightful Heir to the Keys of the Kingdoms of the Secondary Realm by the Architect - a being that created the Secondary Realm. In the first book, Arthur meets a being from the Secondary Realm called Mister Monday who refuses to acknowledge that Arthur is the Rightful Heir. Arthur defeats Mister Monday and claims Mister Monday's First Key as well as the first part of the Will (a sentient creature that is literally the Architect's Will). In this second book of the series, Arthur finds he can't return to normal life anymore because the other beings of the Secondary Realm that want to own the Keys to the Kingdom are now after him.
Arthur is instructed to find the Second Key which a being called Grim Tuesday has hidden somewhere in his domain, deep down in the Pit of the Far Reaches, which is a pit at the bottom of the Secondary Realm. The story begins with Arthur getting a phone call from the Will saying that now that he has the Mister Monday's keys, he's also inherited Mister Monday's debts to Grim Tuesday. Grim Tuesday wants Arthur to give up the Lower House he inherited from Mister Monday along with Mister Monday's key. To force Arthur to sign these over, he insists on Arthur paying back Mister Monday's debts now. Arthur wakes up to Tuesday morning and finding out that his house has been put for sale by Grim Tuesday's minions. He also finds out that his family suddenly have tons of financial problems. Arthur intends to return to Mister Monday's House, however when instead he ends up at the Pit in the Far Reaches – Grim Tuesday's domain.
Arthur gets recruited to become an indentured worker for Grim Tuesday's Railroad down in the Pit. Arthur meets another indentured servant called Japeth. On their way down to the bottom of the Pit, Arthur lags behind with Japeth until he is separated from the group. Then, one of Arthur's friends, Suzy, finds them. She and Arthur puts on a pair of Ascension wings (wings that only fly upwards) and escape as Grim Tuesday's Train makes its way out of the Pit. Suzy and Arthur end up on the ceiling of the Pit. From the ceiling they can see Grim Tuesday's Treasure Tower and they meet a creature that claims to be one of Grim Tuesday's eyebrow, grown sentient, called Soot. Soot agrees to help them find Grim Tuesday's part of the Will. Arthur and Suzy jump from the ceiling onto the glass top of the Treasure Tower then cut their way into the Tower. Once they get inside, Soot disappears.
Arthur and Suzy meet an old man called Captain Tom. Tom tells Arthur and Suzy that Grim Tuesday's part of the Will is located in a jungle in the middle of a sun that Grim Tuesday has kept inside a bottle. The second part of the Will takes the form of a bear that appears to be asleep. The bear is rather unhelpful. Grim Tuesday catches up with Arthur. The bear decides that Arthur and Grim Tuesday will compete to see who will win the Second Key. Whoever uses the second key to create the best masterpiece wins. Grim Tuesday makes a beautiful metallic tree while Arthur makes a xylophone from his childhood memories. The judge, Captain Tom, determines that Grim Tuesday's work is not original but copied so Arthur wins the second key. Arthur becomes master of the Far Reaches.
Arthur finds out that he has inherited problems that Grim Tuesday was struggling with notably a dam that is supposed to contain Nothing – a substance that destroys everything in its path. This dam is breaking and threatening the existence of the denizens of the Secondary realm. Arthur uses the powers of the second key to fix the dam. Eventually, Arthur will return home and all his family's financial woes will be fixed.
Best part of story, including ending:
I like that the second book explores "Nothing" and how it works - it is a very interesting and creative force to reckon with.
Best scene in story:
My favorite scene is when Arthur tries to wake up the second part of the Will and the Will's personality is so uppity and fussy.
Opinion about the main character:
I like that Arthur is like just any other kid and he just wants to be left alone but unfortunately he has been chosen to inherit the keys to the kingdom.