To activate the Emperor's Throne, Tritannus must obtain the seals for the throne's missing pillars. When he takes the seal from the Pillar of Light, the planet's light is fading away, and it is up to the Winx to restore order.
Now in control of the Pillar of Light, Tritannus plunges Magix into darkness, but the Winx Club retaliates with Sirenix and King Neptune's sword.
Tritannus is angry because the Emperor's Throne is not providing him the power he wants and soon discovers the legs of the throne were broken. He then gets an idea of how to activate the throne. Tritannus takes the seal from the mystical Pillar of Light. The whole Magic Dimension is plunged into darkness. Solaria is the most affected, especially by King Radius who gets sick because of his connection to the sun.
At Alfea, The Winx minus Aisha were in the virtual chamber, swimming through an ocean setting trying to locate the circle reef. They come across it, but were confronted by some water dragons that began to darken the area. Bloom tells Stella to disperse the darkness with her light powers, but she just froze on the spot. The virtual environment dissipated and the girls were called to the control room by Faragonda. Obviously, the exercise was a failure.
Faragonda asked Stella what happened, and she could not give an answer. Faragonda fears for the Winx as the simulation was just a pale imitation of what they will face, and if they could not handle this, they will not survive long. She dismisses them for the moment. Stella was filled with self-loathing for screwing up, but Bloom tells her not to worry about it. Musa then wonders how Aisha is doing.
On Andros, Aisha reunites with her parents and tells them of what Tritannus has done to their underwater family. King Teredor then presents Aisha with her uncle King Neptune's sword, which would give Aisha an edge in battle.
Storing it in subspace, as princess of Andros Aisha vows to stop Tritannus and save her family.
In the Infinite Ocean, Tritannus, the Trix, and the mutants find the Pillar of Light, one of the Pillars of the Infinite Ocean that stabilizes the whole Magic Dimension. Tritannus plots to steal the seals to restore the throne and become the emperor of the Magic Dimension, with Icy as his empress. Darcy again shows her displeasure about the whole thing as she and Stormy are practically tossed aside. Before they could take its seal, they were confronted by some guardian Selkies. Unfortunately, the guardians were no match for Tritannus and the Trix.
At Alfea, the girls try to find a way to restore Aisha's family back to normal. Stella calls upon her Sirenix Guardian to ask how. She responds that once Stella opens her heart to her powers, her light will shine. When the Guardian leaves, the room suddenly became dark. It was not just the room as they found out that it was getting dark all over Alfea. The sun was getting eclipsed.
Even then, it was not limited to Alfea. On Domino, Oritel and Marion look at the eclipse in horror. On Eraklyon, Erendor looked at the eclipse in worry. On Andros, Aisha became horrified as the eclipse was causing the oceans to go wild, tossing some unfortunate mermaids about. King Teredor deduced that one of the pillars of the Infinite Ocean were being tampered with.
At Alfea, Faragonda informed the Winx that the sun is getting eclipsed by a dark power, which is beginning to affect the whole Magic Dimension. Stella became horrified as it will no doubt affect Solaria as well. Without the sun, her father, King Radius, will die. They immediately head for Solaria.
On Solaria, Stella's estranged mother, Queen Luna, looked up in horror at the solar eclipse and immediately ran to Radius' chamber, worried for his condition. He coldly tells her that it is nothing as Solaria has two suns, so there is nothing to worry about. Unfortunately, he began to spasm and collapsed, much to Luna's horror.
Soon, the Winx arrive on Solaria. Stella was surprised to find her mother there and asked about Radius' condition. Luna gives her the bad news that he is sick in bed and there is no telling how long he can last without the sun, causing Stella to break down in tears. Aisha then calls, informing them that Tritannus has struck in the Infinite Ocean. They all transform to their Sirenix forms and rendezvous with Aisha in the Infinite Ocean. They are met by the Selkies who lead them to the Pillar of Light where a fight ensues.
Flora, Musa, and Tecna immediately take down Darcy and Stormy. Bloom fights against Icy. Aisha faces Tritannus, who then noticed the seal in his hand. Seeing that he was no match for Aisha's tenacity, he once again used his mutant slaves as shields, knowing Aisha would not fight back against them, Stella then comes in to fight them. Recalling what her Sirenix Guardian said, she used her powers to repel the mutants without killing them, making Tritannus scream in disbelief. While he was distracted, Bloom fires a spell at him to take him down. To her and everyone else' surprise, Icy jumps in and takes the blow, getting critically injured in the process. Tritannus gets angry and promises painful retribution for what happened.
- Tritannus takes the seal from the Pillar of Light to activate the Emperor's Throne.
- King Teredor and King Radius appear for the first time since Season 3.
- King Radius falls ill due to lack of sunlight on Solaria
- Queen Luna, Stella's estranged mother, makes her first appearance since her cameo in the first season.
- Aisha is now equipped with King Neptune's sword.
- Icy takes a direct hit for Tritannus.
- The Eclipse affects not just only Solaria, but also Andros, Magix, Domino, and Eraklyon.
- Stella used her special Sirenix spell, Light of Sirenix.
- Tornado - Used by Stormy against the Guardian Selkies.
- Dark Lightning - Used by Darcy against the Guardian Selkies.
- Hypno Wave - Used by Darcy against the Guardian Selkies.
- Petal Hurricane - Used by Flora in a convergence with Desiryee against Darcy and Stormy.
- Blizzard - Used by Icy against the Guardian Selkies.
- Spreading Fire - Used by Bloom against Icy.
- Ice Prism - Used by Icy to defend herself.
- Digital Strike - Used against Darcy.
- Deafening Chord - Used against Stormy.
- Blinding Ray - Planned to use against the mutants but later aborted.
- Light of Sirenix - Used by Stella against the Mutants.
- Lava Jab - Used by Bloom against Tritannus.
- When the Winx transform into their Sirenix forms, their 3D Sirenix transformation is shown, even though that they transformed on Solaria. They did, however, teleport into the Infinite Ocean immediately after they transformed, which could explain why their 3D Sirenix transformaton was shown.
- This is the first physical appearance of Queen Luna, Stella's mother.
- This is the second time Aisha transformed alone. The first was when she earned her Enchantix.
- The way that Bloom fired her attack on Tritannus, but was blocked by Icy, is much similar to how Icy fired her attack on Bloom, but was blocked by Sky in "Return to Alfea".
- The Second Sun of Solaria makes its second appearance and Radius his fourth. Both appeared last in Season 3.
- It appears that Magix, Domino's palace, Solarian palace, Andros' palace and Eraklyon's palace are in the same time zone in their planets.
- The alternative title for this episode is "Nabu's Return".
- In one scene, Musa's hair is blue when it should be purple with orange streaks.
“By King Neptune's sword, I vow that I won't rest, until Tritannus is driven from the Infinite Ocean.”
“That did not just happen.”