Previous book: Year Three.

This is the fourth book in the "Demigods Academy" series, which follows 20 years Melany Richmonds, who enters the Demigods Academy and is recruited by Hades. Hades reveals to her that Zeus and his followers share a sinister plan to cause havoc on earth in order for humanity to worship the gods as saviours. After the great battles of the gods, in which Zeus and Hades perished and Ares and Aphrodite were defeated and locked in Tartarus, Melany Richmond is struck with grief. She and her friends are hailed as heroes. Melany is particularly lauded by the people of Pecunia, her hometown, "She's the Dark Angel of Pecunia." [location 257].

They have all become demi-gods yet Melany does not feel like a hero.

While the academy is slowly rebuilding, returning to its glory days with Prometheus back as headmaster, Melany longs for Hades and cannot console her hurting soul. Although Lucian and her friends try to comfort her, Melany becomes even more bitter and upset. She cannot believe Hades is truly gone. 

One night, in a dream, she arrives at Elysium and faces Persephone again. Persephone tells her that Hades is not there but suddenly starts to shiver and disappear. Melany is terrified at this sight and wakes up, feeling that something is very wrong but is not sure what. She does not understand where Hades could have gone to and hopes he might be still alive somewhere.

Meanwhile, new recruits arrive to the academy, yet Melany feels a strange and horrifying feeling coming from one of them. She has another dream, in which she sees the Fates. The Fates in her dream are scared, speaking of someone who tries to revive a god and enter their domain.

Melany feels she must solve this matter and she believes the answers lie with Thanatos, the god of death. In her dreams, she hears the words "threads" and "times" and wishes to understand more. 

Lucian also has a dream in which he meets his brother Owen, who is supposedly on Olympus. Owen tells him that something is not right with the time on Olympus, that something is very wrong but disappears without explaining. 

Strange phenomena keep happening. Hephaestus receives an empty list for the next shadowbox (which never occurred before), which means no new recruits for the academy for the following year. The shadowboxes are special boxes which every 18-years-old on earth receives and inside there might be a letter of recruitment to the academy. Melany learns that the Fates prepare the list, hence she is even more determined to find out what is going on.

Melany decides to speak to Thanatos and asks the Furies to help her find him. Meanwhile, it turns out that the new recruit, Cassandra, has extraordinary prophetic powers and she might have caused the mysterious dreams. Another recruit, Flynn, turns out to be Empusa, a demon sent by Aphrodite to hurt Melany.

In the end, Melany locates Thanatos (with the help of Tisiphone) at Nyx's palace, yet Nyx refuses to let her meet him. Melany sneaks around and finds him sitting with his brother, Hypnos. Thanatos tells her that people on earth have stopped dying and he is not sure what is going on. He tells her the Fates might know, but that they live in the Cave of Memory which is a mysterious place whose location is unknown, except to Aphrodite. Therefore, Melany decides to travel to Tartarus and ask her. At this moment Nyx discovers her and threatens her, ending the book with a cliff hanger.

In this book, Melany is undergoing a process of grieving after the loss of Hades, who had been her mentor – see book 2 in the series. She refuses to acknowledge his demise and although she is constantly told that he is dead, she cannot (or will not) believe it. She longingly searches for him, unable to move on with her life. The book shows how difficult it is to cope with the loss of a loved one and how it is okay not to feel okay. Everyone needs their own time to heal.

The gods are less dominant in the current story since after the war of the gods their role in the plot has diminished. The book focuses more on Melany's search of Hades as well as for answer for the new mysterious threads of life. Melany does not know if she can trust any of the gods at all.

In the world of this book, the gods are mischievous, suspicious and they can even die. Except for their powers, they do not exhibit any moral values. Can humans truly trust such gods/ apparently humans must trust themselves, although we should not forget that Melany is now a demigod herself.

It is also left for another book to reveal the true force and purpose of Cassandra. It appears that, unlike her mythological counterpart, this Cassandra is well respected. Apollo is in awe of her prophetic prowess. The readers who are familiar with the myth of Cassandra may appreciate this change, perhaps redemption for the Trojan princess who suffered greatly.

As a closure of her previous life on earth, during the honorary ceremony in Pecunia Melany meets Callie Demos and her mother, in whose estate she lived with her aunt. She also visits her aunt/adoptive mother Sophia's grave, thus, parting with her old, mortal life, after becoming a demigod. Melany thus forsakes her mortal relations and can move on to focus on the divine world.

In the previous books, Melany felt estranged from her friends, especially after leaving the academy to train with Hades. His loss deepens her feeling of loneliness and alienation. She emphasizes the stark difference between them, "I was the raven to their doves" [location 76]. Her guilt towards her friends intensifies since she had not found a way to return their powers to them yet and at the same time she is torn internally due to all the elements she now possesses, leaving her in constant pain. Melany confesses to herself, "I wasn't a hero. I most definitely didn't feel like one. I felt lost and hollow. Empty" [location 100]. The focus on Melany's grieving process shows the readers that you can feel sad and alone and it is completely okay you do not need to put on a false happy face and reassure everyone that you are fine. You must cope with your sadness and take all the time that you need.

The new search for Thanatos and the Fates provides Melany with a reason to continue and find a meaning for her life without Hades, perhaps even a slight hope of bringing him back from wherever he went to. Thus, Melany prepares for her katabasis to Tartarus in order to find answers which will be revealed in the next volume.

While in real life we cannot bring our loved ones back, suck books are escapism, a fantasy of "what if." It is a dream shared by the audience as well as by Melany. The readers may cheer Melany on, hoping for her success in bringing Hades back. The fact that he is a god may make his return from the dead more acceptable.